How to Control and Get Rid of Pond Algae

Although algae may be a potential source of biofuels for our next-generations, it can sometimes be a nuisance to pond keepers/owners. Without proper planning and prior knowledge, controlling pond algae can prove to be a daunting task. If you have tried it before, you definitely know what I mean.

In high density, algae blooms can cause poisoning, depletes oxygen in a pond and also causes water discolouration. This will, in turn, affect the water quality thereby making it unsafe for animals, fishing, swimming, etc.

However, in this article, we’ll be looking at several effective and efficient ways you can use to control and also get rid of any algae that grow in your pond. We aim to guide and help you learn the best ways to deal with algae growth as a pond keeper/owner.

Here is what you should consider when deciding how to get rid of pond algae. Read on to find out more:

Table of Contents

The equipment for controlling pond algae

Almost all new ponds lack proper balance of animal life, plant life as well as other common biological functions. This makes combating algae a major problem for any new pond keeper/owner. The new Pond keepers/owners will have to search for ways to combat the algae, making algae control the most discussed topic among new pond owners.

The first and most essential step towards an algae-free new pond is to use proper and appropriate equipment throughout the whole algae control process. For instance, when installing a pump in your pond, it should be capable of moving about half of the volume of the pond to create a water garden, take a look at our range of recommended solar pond pumps.

A water garden is a pond that contains a lot of fish and also other plants. However, there are other types of ponds that contain a lot of fish but very few plants and thus need more filtration as compared to a water garden. A good example of such a pond is the koi pond.

For the koi pond, it’s advisable to move the entire volume of the pond per hour. In addition to moving the large volume of water, ensure it undergoes filtration. The pump you use should be able to pass water through a filter that is sizable depending on your pond size.

There is a guide to selecting the perfect combination of filters as per your pond size. Note that biological filtration usually takes several weeks if not months to fully mature to a point where it can make a significant improvement to the quality of water in your pond. Filters should run 24/7, nonstop, for the filtration process to work.

Additionally, during the winter you’ll want to make sure that you’re using a pond heater & de-icer to prevent the accumulation of harmful gases in the pond water.

How to construct the perfect pond

Take a read of our 7-step guide on how to build a small pond in your back garden.

However, as a rule-of-thumb, for clean, high-quality water, the construction of a pond is an essential factor that must be considered. Here is what you should keep in mind:

• A pond has to have roughly 40% of its entire surface as a deep zone. This deep zone is supposed to be 3 feet or even more for koi ponds and 2 feet for a water garden.

• 30 % of the pond needs to be at an intermediate depth while another 30 % should be about 1 to 1 feet deep

• For easier removal of pond debris, it’s recommended that the pond should have a slight slope.

• Always use Pond skimmer to remove up to 85% of your pond debris before it sinks, and make sure that you use a high-quality pond liner.

To avoid rainwater from flowing over your yard and into the pond, you should be keen and careful during the construction process. Rainwater flowing into ponds is among the most common reasons for the growth of algae. This is because rainwater brings about runoff water that erodes and carries several organic remains that may contain major nutrients that feed and help the algae thrive.

Besides, chemicals and fertilizer will be eroded into the ponds leading to even bigger problems. It is possible to alter the surrounding of your pond to ensure water runoffs don’t flow into it even if you have already constructed one. However, you can’t do anything about your pond depth if you have already finished constructing it.

Reduction of algae levels requires that you don’t build ponds using marble or limestone. This is because marble and limestone contain high pH that can cause more algae growth.

How to maintain your pond, to prevent the forming of algae

It’s a normal procedure for you to maintain your pond now and then. It’s also normal to notice a buildup of debris at the bottom of your pond. If the sludge buildup doesn’t exceed about ¼ inch, it’s not necessary to consider physical removal.

If you had constructed your pond properly, most of this debris would recollect into a small area which will be easy to remove. You can use a net to remove dead leaves and other course materials, i.e., string algae. In case the debris is very fine that a net can’t remove it, use a pond vacuum.

There are several products that you can use to reduce sludge in your pond. For example, you can use enzyme and bacteria products such as PondZyme, Simply Clear, EcoFix or other products from Microbe-Lift to improve fish conditions, reduce pond odor, improve the general water quality as well as reduce the quantity of sludge that may lead to algae growth.

Pond maintenance varies from time to time according to different seasons. For instance, there is a lot of work that needs to be done to the pond during summer and spring. During winter and autumn, you only have to make the pond livable by not allowing fish to hibernate due to freezing.

Number and type of plants in the pond

In case you don’t have a koi pond, ensure you have the right number and type of plants in your water garden. Plants like Anacharis, floating plants and other underwater plants get rid of excess nutrients found in the pond. They do this by absorbing the nutrients for self-gain and growth, hence algae starves because its source of food is no more.

Cover about 2/3 of your pond surface using plants that make the pond water surface shaded. Good examples include water lilies and floaters, i.e., Water Hyacinth, Water Lettuce, etc. By covering the water surface, these plants minimize the penetration of sunlight into the pond which, in turn, starves algae due to inadequate sunlight and also helps in keeping the pond water cool.

It’s worth noting that algae could be still present in your pond even if you use the right type and number of plants as well as proper components, but you don’t have a lot of fish. This happens mostly when the pond is quite young. During the first years of a young pond, you can use other methods to control algae. If the pond isn’t entirely emptied and refilled, as years go by and it matures, the presence of algae reduces.

Pond algae treatment procedure

For proper pond algae treatment, pond keepers/owners should use beneficial enzyme and bacterial products as earlier mentioned. This should be done regularly while the pond matures. In case you have some issues with green water, install an ultraviolet sterilizer. An ultraviolet sterilizer guarantees you 100% clean water as the pond matures.

Here are some products you can use in treating pond algae:

i. Using GreenClean for Filamentous algae

There are several types of algae, i.e., filamentous algae, planktonic algae, macrophytes algae, etc. However, Filamentous algae are the most common of all the others. This type of algae is mostly found attached to sticks, leaves, mud, rocks or other plants. As it grows, it stretches out to the surface, breaks up and causes new growth that is then transported throughout the pond by wave and wind action.

Filamentous algae occur in many forms, e.g., shot and furry, stringy and long and even in the shape of a mat or a web. It’s the short algae that usually covers almost everything in a pond. It’s velvet in color and very beneficial because it makes the pond look natural. It produces oxygen during the day, and most fish depend on it although it uses nutrients from pond water.

Filamentous algae can’t be eliminated at once with plants and fish in the pond. String algae are even harder to deal with because it can even coat an entire waterfall. Nonetheless, where possible, it can be removed physically from the pond. Due to the high intensity of sunlight on shallow streams and waterfall, filamentous algae will most likely thrive. This is because the sun will be providing more light and heat as well as constant nutrient supply flowing through the waterfall or shallow stream.

The best and most effective way to treat filamentous algae found on streams and waterfall is using GreenClean. It fights and prevents algae from blooming as well as releasing essential oxygen to pond water while it biodegrades. It is formulated without the use of chlorine or any other harsh chemicals to ensure they don’t affect the aquatic ecosystem negatively.

ii. Using Algaway

While your pond is maturing, Algaway is a very useful product in controlling algae. Algaway is an algaecide that helps control string algae. However, you should not use Algaaway in ponds that contain ornamental snails, mollusks, shrimps and other crustaceans.

This algaecide is meant for self-contained fountains and ornamental ponds that don’t have an outflow. Before the addition of Algaway to a small pond that has excess algae, ensure you clean off some excess algae. This will help you minimize the quantity of organically decaying matter.

iii. Using Barley Straw

Use of Barley Straw, as well as Barley Straw Extract, is also useful and efficient in improving the conditions of water in ponds. Barley Straw doesn’t kill previously existing algae. Instead, it inhibits the growth of new algae, making it very effective for use in new ponds.

Although it’s not clear how Barley Straw works, it’s believed to produce some chemicals that prevent the growth of algae. This occurs due to oxygen presence and when it’s exposed to sunlight. Barley Straw doesn’t affect other aquatic plant growth at all.

When it’s applied to a pond that has cold water, for example, less than 50F, the Straw will take 6 to 8 weeks for it to start producing the chemical that inhibits the growth of algae. If applied to warmer water, for example, 70F and above, it will probably become effective in 2-3 weeks.

You should apply about 2 to 3 bales of Barley Straw per acre of the pond. This translates to about 10-25 grams for every square meter of the pond area. The pond water depth isn’t necessarily important when applying Barley Straw.

iv. Using pond dye

Pond dyes work by helping color water blue-green or dark-blue. This coloring creates a shade for the pond water hence reducing the quantity of sunlight absorbed by algae. Black and blue dye are the best for use in lakes and large ponds due to low cost although it can also be used in other smaller ponds.

Note that Black dye may not help you if your pond is muddy because it might not penetrate suspended articles. However, a blue dye can readily penetrate suspended particles.

v. Using Fountec

Fountec improves the quality of pond water by keeping it clean as well as removing algae. In case your pond doesn’t have fish yet, this is an excellent product to use because it’s safe for other animals, e.g., pets that may drink water from the pond. However, it’s not safe for fish.

vi. Using pond Ionizer

This is among the most recent algae control products. A pond ionizer uses electric charges that run through an anode that is made of copper. The anode is placed in a line of water flow where it releases copper ions that minimize the growth of algae.

Whenever you are treating algae, it’s critical to make sure you abide by the product package directions and ensure there is adequate aeration in the pond. Besides, you should not overfeed fish or add a lot of fish that your filter and pond can’t support.


Do you now know how to control pond algae? Simple, isn’t it? With the right knowledge and proper planning, algae control will be quite simple. You should note that fish foods and fish themselves add nutrients to ponds. These are the nutrients that feed algae.

In summary, here are some points to note from this article:

• Sludge that is less than ¼ inch at the bottom of a pond should not worry you. Always keep down organic load in the pond by keeping any runoff out and also vacuuming any already accumulated sludge.

• There should be no overfeeding or keeping a lot of fish than the pond can support

• Ensure you install a bigger biological filter and allow some time, i.e., several months, for it to work.

• The aquatic plants you use should be able to act as floaters, shade as well as underwater plants to help in getting rid of excess nutrients. These plants should be of the right type and amount.

• Always use biological treatment methods and allow them some time to work effectively. Remember, some of the outlined methods, e.g., Microbe-Lift in this article take time.

• Barley Straw Extract is used in ponds with not more than 3000 gallons while Algaway is used to get rid of existing algae problems pretty fast.

• Always install and use the ultraviolet sterilizer to effectively control green water algae.

How To Get Rid Of Algae In Pond

Pond Algae Control & Removal

As the summer months roll on, pond algae control is an extremely important part of maintaining a healthy body of water. When algae starts to take over your lakeshore, it will discolor the water and suck out the oxygen, asphyxiating other life forms. Certain types of algae are even toxic to humans and pets. When you see excessive algae growth it is a sure indication that you have problems with your water quality. Your shoreline area will become unsuitable for fish, important aquatic organisms, other animals and for activities such as swimming and fishing.

Here are are few pond algae solutions and treatment to help you get rid of algae in a pond or lake

There are numerous ways to deal with the types of algae that may be causing you issues in your body of water. Below we will talk about:

  • Manual Pond Algae Control Tools
  • Automated & Machines that control algae
  • All Natural Products
  • And the best algaecides for killing algae

Using any of the following pond algae control products alone or in combination with each other to get rid of pond / lake algae and then using proactive prevention solutions will help reduce future growth.

The top products for manually removing algae from your pond or lake: Using an Algae skimmer net is one great option for removing it from the surface. The

skimmer makes it easy to quickly clear an area and maintain it. Like floating weeds, when algae dies and sinks to the bottom of the water, it will decompose and will contribute to a new layer of muck. Collecting algae at the surface is the perfect preventative measure to combat this sludge accumulation on your beach.

Our Long Reach Rake will also work to skim algae because of the detachable float but has the added benefit of being label to collect what has been pulled in as well as clean up on the bottom of your shoreline.

Automated Pond Algae Control Products: Our top choice for Automated Algae Control is the AquaThruster. This product works for algae, weeds & muck in the way that a leaf blower works for leaves in your yard. It creates a powerful current water flow on the surface that blows and pushes suspended algae and weeds far away from your shoreline. It also helps in preventing and protecting your area from more floating in. People use the AquaThruster in their ponds both as a solution to algae, sea weed and sludge along with it being a preventative measure. In smaller ponds, the AquaThruster is great because it can help move everything to the edges of the shoreline so that it is much easier to collect and get rid of with a rake or pitch fork.

Another excellent completely labor free algae solutions is The Airstream Pro. It combines the powerful circulation of the AquaThruster but also adds high volume aeration. With proper aeration, this effectively reduces the phosphorus, nitrogen and carbon that lead to excessive weed and algae growth. The Airstream and items such as Aerating Fountains are perfect for lake shore owners looking to reduce the algae because of the aeration they provide which combats weeds and muck and to reverse the water stagnation in channels, coves and bays through the use of aeration.

Chemical and All Natural Pond Algae Solutions

When using an algeacide to combat algae in your lake or pond, a product like Cutrine Plus works great and is EPA approved for use in drinking water reservoirs, irrigation conveyance systems such as canals and ditches and of course in your body of water. We suggest using our copper algaecide Cutrine Plus & Bio-Chemical Catalyst Combo Pack to increase effectiveness and allow for less chemical us. For even better results try using Cutrine with both Liquid Bacteria & Bio-Chemical Catalyst to improve and speed up the process of eliminating algae. You can also purchase a combo pack to take care of all your algae needs.

Whether you have large amounts of algae already or are looking to take the necessary steps to keep it from showing up, it is important to identify the factors that cause algae to thrive and eliminate them. Equally important is using the proper tools, products and methods to assist you in taking preventative measures along with maintaining your lake or pond to have a healthy and thriving body of water.

There is nothing more disheartening than watching your water column turn green with planktonic algae, turning the water into a green colored scum. Or watching the filamentous algae, with its thick, green hair-like strands building up on your shoreline or on the waterfall feature of your pond. A pond or lake with this kind of algae buildup, with plenty of nutrients and the summer sunlight helping feed it, will quickly take over. Read more about the two main types of algae in a previous article in our Learning Center.

How Do I Get Rid Of Blanket Weed In My Pond?

Getting rid of Blanket Weed in your garden pond can feel like a never-ending battle. See our post on how to banish Blanket Weed and get crystal clear water again.

Blanket weed causes and treating phosphates

There are many Blanket Weed remedies but first, you need to understand the causes:

  1. Plants, plants and more plants! Any and all pond plants will help absorb additional phosphates within the ponds water system.

  2. Phosphate sponges – these have a limited lifespan but will work overtime to help reduce all levels of phosphate within your water supply.

  3. Water changes – Possibly the cheapest method of removing phosphates. But be careful! Some local tap water supplies can themselves contain high levels, so be sure to test before using this as an option!

These are the main causes of exponential blanket weed growth. Any steps taken to remove phosphates, or restrict them from your water system is always beneficial as whilst there is not a high-risk factor to fish, all forms of plant life will thrive so it is best to avoid letting too much getting to your pond. Sunlight

Excess exposure to sunlight provides vital energy to all forms of algae to perform photosynthesis, which means that tackling blanket weed whilst the sun is shining is a never-ending project. It is vital to make sure that your pond has some shade or that you have plants such as lilies that cover some of the surface water. It is key to remember that when treating your pond in sunny weather with our blanket weed treatment, to double the dose to see a difference. Perhaps building partial decking cover?!

Blanket Weed Treatments

The best method with all treatments is to remove as much as possible before adding anything to the water. It’s a simple point of exposure. If you treat a pond full of blanket weed with 500ml of treatment, then that is going to have a harder time battling if you were to treat a freshly pruned pond with the same amount making it a much more concentrated attack on the blanket weed itself.

Barley Straw is a cheap and sustainable alternative to most treatments without any worry of overdose. It is generally advised that it is added to the pond system late February early March as it requires a germination period (4-6 weeks) within the water as the enzymes saturation the pond.

Your other option, and by far the most effective in the long run, is chemical treatments. But they offer a much more direct impact on the blanket weed without a need to wait around for gestation. Our very own Pond Rescue Blanket Weed treatment offers a fast-acting relief for blanket weed by using enzymes to tackle the problem face on without harming your fish.

What is Blanket Weed: Your Questions Answered

Posted by CD Aquatics on Apr 17 2018

What is blanket weed and why does it grow?

Also known as pondweed or ‘water silk’, Blanket weed is filamentous type of pond algae that forms a hairy green blanket across your garden pond, turning the water green along with it.

Ponds that are situated in an area that get a lot of sun are likely to be more problematic, however it can be brought to your pond by birds, insects or even blow in by the wind, and once it’s in there it quickly thrives.

High phosphate and nitrate levels along with waste created by organics in your pond such as fish waste, uneaten food, rotting leaves and plants can all add to the problem by providing a source of growth to the blanket weed, so regular pond maintenance to remove such elements can help.

Is blanket weed bad or harmful? Can it kill fish?

Blanket weed and the green pond water that comes with it doesn’t just look very unsightly, it is also bad because, though it doesn’t harm fish directly, it can cause them problems in many ways. Blanket weed can cause pond pumps and pond filters to block, especially in fishponds where there are a lot of fish, which leads to a build-up of fish waste and creates an unhealthy environment. Other blanket weed related problems include fish becoming tangled in the weed and not being able to back out, and low oxygen levels due to large quantities of algae.

How to control, reduce, or remove blanket weed – which blanket weed treatment is the best?

The best way to control blanket weed is, firstly, to keep on top of it. It is unlikely to go away on its own and can become a major job if not dealt with – treat it and maintain it.

A Blanket Weed Remover Brush can be useful to remove excessive strands of blanket weed, these come with an extendable handle to provide a longer reach, and by using these to remove as much as possible will reduce the amount that is going to end up in your filter when you apply the Blanket Weed Treatment (Blanket weed killer) to get rid of any that remains, as once the treatment has killed it off it is often pushed into the filter where it will need to be removed, and you could be doing this for several days.

To stop blanket weed and other pond algae from taking over your pond, treatments should be used during the main season to keep it at bay, as they are best used as preventative methods rather than a cure.

If you’re in search of a more powerful solution to how to treat blanket weed, try an easy-to-install Electronic Blanket Weed Controller, which uses modern design and technology for long lasting and effective control of blanket weed.

For more information on pond algae maintenance in general, check out How to Control Pond Algae.

How To Remove Blanket Weed

Blanket weed is a major problem in ponds, not only does it look unappealing but it can also overwhelm plants and pond life you may have in your garden. Not only this but it can also be a sign of imbalance in your pond, so eliminating it before it takes hold is essential.

Any keen aquatic enthusiast knows how detrimental blanket weed can be to a pond, however if you’re unfamiliar with this major pond problem then keep reading to find out more.

What is blanket weed and where does it come from?

There are around 20,000 different forms of algae with over 500 species under the umbrella of blanket weed or string algae as it is also known. Blanket weed is a hair like algae that consists of long green fibres which grow rapidly and if left untreated will quickly spread throughout a pond. This form of algae can either free float on the ponds surface or cling to the pond walls, rocks and plants.

Just like all forms of algae, blanket weed reproduces through spores. These spores are present in the air and can also be carried from pond to pond on birds, amphibians and plants.

How do I remove blanket weed from my pond?

If you find that your pond is affected by blanket weed then it is a sign that your pond is not balanced. The most cost effective way to control blanket weed is to help everything in the pond reach the right balance. It is important to remember that a pond is a mini eco-system, each element within the pond combines to balance it as a whole.

We would advise ensuring your pond has enough plants within it, as these will use the excess nutrients that can lead to blanket weed building up in your garden pond. It is important to have the right balance of plants in your pond, so aim to mix up oxygenators, marginal and deep water plants. The use of phosphate removers/absorbers provide an alternative method of removing these excess nutrients in ponds where plants are not an option.

If you find that blanket weed is an extreme problem in your pond, why not try one of our blanket weed removal products? This selection of handy treatments provide a temporary solution to the problem, so it is vital you look to balancing the problem from the root. Once the pond has been treated you can then look to balancing your pond correctly to ensure the problem does not return.

Why does blanket weed keep coming back to my pond?

If you’ve used a treatment to remove blanket weed from your pond, then it is vital you create the right balance in your pond after this. If you fail to do this, you can guarantee the problem will reoccur.

  • Keep the amount of fish in your pond to a minimum as waste from pond life can increase the nutrient level in the water causing algae to build up.
  • Remove any rotten vegetation, including dead leaves, although these seem like small issues they can unbalance the levels in the water again boosting the nutrient levels.
  • Regularly maintain pond filters to remove uneaten fish food, fish waste and other debris which all contribute to excess nutrient levels.
  • Ensure all plants in your pond are healthy and thriving. Again this may seem like a simple step but it can really make the difference between a healthy and unhealthy pond.
  • In ponds where plants are not an option use phosphate removers to artificially reduce the excess nutrients to cut off the blanket weeds source of food.

Are plants good at controlling blanket weed? And if so which plants?

Plants are an excellent way to balance your pond, they can thrive on high levels of nutrients and can be key indicator as to whether your pond is healthy or not.

Rorippa Nasturtium Aquaticum or Water Cress as it is commonly known is an excellent choice if you have issues with blanket weed. This plant will only grow where there is a high level of nutrients in the water. Meaning when the balance is corrected the plant will gradually shrink, helping you know you’ve achieved a good balance.

Pond Lilies are also a great idea as blanket weed thrives on sunlight. By adding pond lilies to your pond these will reduce sunlight levels as well as absorbing nutrients which otherwise the blanket weed would use to thrive. They also provide shade and shelter for you fish.

For more pond ideas, why not check out our range of pond filters & pumps, pond treatments and much more online at Pond Planet.

Stop Blanketweed!

Eradicates blanket weed in ponds

STOP Blanketweed is an effective treatment of filamentous algae, commonly known as blanket weed in ornamental and garden ponds. Blanket weed is one of the most hated problems of pond keeping and a nuisance to everyone as it makes your pond unsightly, blocks filters, pumps and pipes. STOP Blanketweed is a unique product which will successfully eradicate blanket weed when used as instructed.

1kg (Treats up to 10,000 litres / 2,200 Gallons)

2.5kg (Treats up to 25,000 litres / 5,500 Gallons)

4kg (Treats up to 40,000 litres / 8,800 Gallons) HSE No. 9647

Dosage Instructions

• Apply 30 grams (one scoop) of powder per 900 litres / 198 gallons of water.

• Mix the powder thoroughly with pond water in a suitable clean container.

• Now distribute this mixture evenly over the pond surface.

• Add this dose once per week until the blanket weed has gone, usually after 3 weeks.

• One or two additional doses may be needed in some ponds.

• Continue to dose once a month to prevent the blanket weed returning.

• If water temperature is below 8°C, treatment efficiency is reduced.

There are over 20 000 different species of algae of which Blanket weed is one type.With so many species it can be quite a challenge to differentiate between them. Blanket weed, however is the most common type found in garden ponds and is easily identified by its long filamentous threads. It has the potential to grow more than 2 meters in a day. With such a rapid growth rate, if not treated quickly enough it has the potential to cover your pond and block the filtration system. Prevention is certainly better than having to deal with the potentially fatal consequences of blanket weed by depriving fish and other aquatic inhabitants of oxygen.

Why is blanket weed common to garden ponds?

Blanket weed is a thread-like, filamentous algae that floats on the water. It forms a dense hair-like green mat attaching itself to rocks or to the side of the pond. If it attaches itself to oxygenating plants the algae will smother the plants preventing them from releasing oxygen into the water.

Blanket weed thrives on sunlight and nutrients in the water. The higher the levels of organic matter the greater the chances of having to deal with this green filamentous algae.

  1. Pond over populated with fish – this will lead high levels fish faeces increasing the organic nutrients levels in the water
  2. Incorrect pond pump and filter capacity for pond size
  3. Dead leaves and plant matter falling into the pond and left to turn to nutrient-rich sludge at the bottom of the pond
  4. Pond exposed to fully daily sun light
  5. Fertilizer leached into the pond via rainwater run-off from surrounding landscape

Any one of these five will increase the nutrient content in your pond. Blanket weed thrives on nutrients so it you want to reduce the risk of blanket weed then avoid nutrients entering the water.

How to reduce the risk of blanket weed

  • Remove plant debris before it sinks to the bottom (particularly during the autumn months) by securing a net over your pond to catch the leaves or regularly skimming-off fallen debris
  • Avoid the use of fertilizers on your lawn
  • Top-up pond water levels with rainwater rather than tap water as the former is believed to have less nutrients such as calcium
  • Pot plants in low nutrient aquatic soil only
  • Add water lilies to your pond. They add shade and protection for fish and other aquatic inhabitants. They also use-up nutrients leaving little for blanket weed to thrive off
  • Avoid over feeding fish. Uneaten food will turn to sludge and increase water nutrient levels
  • Remove sludge from the bottom of your pond – the result of decaying plants, fallen leaves and fish waste left to rot. This can be done by vacuuming the bottom of your pond

There are various treatments available from aquatic stores to treat blanket weed. For garden ponds home to gold fish or aquatic plants only then the introduction of pond snails is a wise choice. Snails will eat pond algae such as blanket weed, uneaten fish food and decaying matter. They are recognised as an ecologically safe way to control algae without the use of chemicals. For Koi ponds, use barley straw logs to rid your pond of algae.

The positive effects of blanket weed

While high levels of blanket weed can be disastrous to your pond, in small concentrations they actually have the ability to cleanse and purify the water by using up organic nutrients present in the water. A pond completely free of algae may not be possible but keeping the nutrient levels low by following the above mentioned 7 points will go along way to a happy, healthy and well balanced pond.

Evolution Aqua Stop Blanketweed

Delivery rates
Standard Delivery weighing under 250g – £2.99
Standard Delivery weighing over 250g – £4.99
48hrs (not including Saturday or Sunday) from £6.99
24hrs – please order before 2pm for next day delivery (not including Saturday or Sunday) from £8.99


Direct dispatch plants under 30kg will be subject to a £7.20 delivery surcharge*. Plants over 30kg, i.e 30ltr Lilies will be subject to a £50 delivery surcharge*.These are sent directly from our supplier make sure the plants you receive are fresh and in great condition. There is no limit on how many you can order for one delivery charge. This is in addition to any other carriage costs for items sent directly from Bradshaws Direct.

Please allow 5 -10 working dates for delivery, reducing to 3-5 working days during the peak season of March -July. (Next day and 48hr not available)

Custom Liners

Custom size liners will be subject to a £10 delivery surcharge* due to being dispatched directly from our supplier.

Please allow 5 -10 working dates for delivery. (Next day and 48hr not available)

Delivery information
Items under 30kg will be sent as parcels. Items over 30kg (Including direct dispatch plants) will be sent as pallets.
The Standard Delivery charge for a large single item weighing over 30kg is £30 (Deliveries to certain locations may cost more)
Items being delivered to Highlands, Islands and Northern Ireland may incur an extra delivery charge. If the cost for postage is different to the above we will contact you to advise you. Your parcel will not be sent out until you have agreed to the delivery charge.
For any delivery enquiries, please email us at

Pond Algae Control

Algae control in ponds is a very important part of maintaining a healthy pond. In very high densities, algae blooms may discolor the water and out-compete, poison, or asphyxiate other life forms. Some algae are toxic to humans and dogs. Excessive algae growth can indicate problems with water quality. Water can become unsuitable for fish, swimming, and other animals.

Nutrient pollution such as excessive nitrogen, phosphorous, carbon, and potassium can originate from fertilizer, farm runoff, septic systems, and decomposing lawn clippings. Prevention along with a proper pond algaecide should be employed for optimum pond algae control.

For pond algae or lake algae control, we recommend the copper based algaecide Mizzen® to help control nearly all types of Planktonic Algae, Filamentus Algae, and Chara. Mizzen® is an EPA approved algaecide that is safe for most fish, however, it is not recommended for use where there are Koi, Trout or Channel Catfish. Simply spray Mizzen® evenly across the surface or spot treat algae mats as needed. No swimming restrictions apply.

There are some products available that will slow the regrowth of algae. Pond control products such as SparKlear® and PhosControl® will reduce the nutrients available to the algae.

If you have any questions or would like to speak to us about pond algae control, please feel free to call us at: 1-877-428-8898

Application Tips:

  • For recurrent algae blooms in your pond or lake, we recommend that you re-apply Mizzen® in 2 – 3 week intervals.
  • For severe algae blooms, avoid oxygen depletion by applying to one half or one third of the area at a time.
    Allow 10 – 14 days between the applications.
  • Break up any large mats of algae before applying the algaecide.
  • Apply Mizzen® when algae first appears, and when the water temperatures are above 60° Fahrenheit.

Refer to label for dosage rates and other instructions.

Identifying Algae

Algae is commonly referred to as “pond scum” or “pond moss” and typically forms greenish mats upon the water’s surface. Algae usually begins its growth along the edges or bottom of the pond and “mushrooms” to the surface buoyed by the oxygen it has produced. Algae can also form fur-like growths on logs, rocks, and even the backs of turtles. The texture of these growths may be slimy, cottony, or coarse.

There are many groups of algae. The green group (clorophyta) has more than 7,000 species in a variety of habitats, including some of the most plant-like.

Algae can be found in almost any habitat on earth as long as moisture is there at some time, even if that time is very short.

Algae differ from most pond plants or lake plants in that they lack roots, leaves and other structures. Algae can essentially be divided into two different physical categories: Planktonic Algae and Filamentous Algae.

Planktonic Algae

While species of planktonic algae can only be indentified under a microscope, abundant growth is easy to identifiy visually. A Planktonic Algae bloom can appear as a paint-like scum on top of the water’s surface. The water column turns green throughout and is often described as “pea soup.”

Planktonic Algae can sometimes be mistaken for other growth, such as Duckweed or Watermeal (two common plants found in ponds and still lake waters). You may easily determine if your waterbody has Duckweed or Watermeal by placing the bottom of a glass jar or drinking glass into the water. Remove the jar or glass. Duckweed will look like little flat leaves with small root hairs. Watermeal will look like small green grains.

Filamentous Algae

Filamentous algae may seem like long stringy hairs, cotton-like in appearance. Individual filaments are a series of cells joined end to end which give the thread-like appearance. Filamentous algae can form thick, greenish looking mats on the water’s surface, and many times it is attached to a substrate such as rocks, logs and other plants.

Some filamentous algae may be bright green and slimy, while some may look more like “horse-hair” with a course texture, like that of steel wool.

Blue-Green Algae (Toxic Algae)

Cyanobacteria, also known as Blue-Green Algae, can contain a harmful bacteria and be dangerous to pets and humans. The scum can often smell like sewage or manure.
Not all blue-green algae is toxic. Cyanobacteria, looks like someone took a can of green paint and dumped it into a body of water. This bacteria can also appear reddish-purple or even brown. It is also known in the marine environment as “red tide.”
Harmful algae blooms can decrease the water quality, produce an awful odor or taste, and cause the production of algal toxins. These toxins could cause serious illness or death. Toxic alga coincides with a lot of sunlight, warm temperatures and slow moving water. It can be problematic if the water is left untreated.


There is one form of algae that resembles submerged plants. The common names for these are Chara and Stonewort.

Chara is very common on the bottom of lakes and ponds. Chara often looks like a matted tangle of plants, forming a carpet on the lake or pond bottom. It has a crusty, course texture and a musky odor when crushed in your hands.

Chara has stem-like braches with forked leaves, and leaf-like structures that are whorled around the stem in fairly uniform intervals. Also look for little bumps or spots on the leaflets.

Chara can only be treated early in its growth cycle. Its course texture later in its growth cycle is caused by the absorbtion of mineral deposits. Once chara has absorbed these materials, it begins to have an innate resistance to algaecide. Because of this, we recommend that chara be treated for early in its growth cycle before it has a chance to absorb these mineral deposits.

Stonewort is similar, but has smooth branches and the stems are more translucent. The leaves also appear to be covered in a green gelatinous substance. Stonewort also lacks the musky odor found with Chara.

Each of these algae varieties is controlled with an algaecide such as Mizzen®.

Pond Algae Control: How To Easily Get Rid Of Pond Algae Like A Pro

by Tory Jon | Last Updated: January 27, 2020

Pond Academy is reader-supported. Buying through links on our site may earn us an affiliate commission. As an Amazon Associate I earn from qualifying purchases.

It can be extremely frustrating watching algae blooms take over your once beautiful pond.

And at first glance, it might seem like a difficult task to clean all that algae up, especially if you’re trying to remove algae from a pond without harming fish.

But, fear not my fellow pond owner, as we’re about to show you the best methods for getting your pond algae under control.

Remember, not all algae is bad, and you’ll never get rid of it all…

But, with a little know-how your algae problems will be a thing of the past!

Psst! Pin This Page For Future Reference

How to Get Rid of Pond Algae

There are multiple ways to get rid of algae from your pond or lake. The best algae control methods for your pond will depend on the types of pond algae you have amongst other factors. And we want to help you find the best solution for your unique pond and situation.

Read through the pros and cons of each solution below and find the right one for you. And feel free to contact us if you have any questions.

UV Pond Clarifiers

Strong ultraviolet (UV) light can damage and destroy algae cells. And UV pond clarifiers work under that principal – they blast pond algae with a strong source of UV light. This “clarifying” process is effective at getting rid of both green and blue-green algae, but is ineffective for larger types of algae like string algae (aka filamentous algae).

UV pond clarifiers are available in several different configurations: they are attached to your pond pump, or alternatively come as part of a pond filter.

Essentially, your ponds pump will circulate the water through the UV pond light, which destroys the algae quickly and easily, thus improving the water quality in the process.

Here’s a super quick video of how our recommended TotalPond UV clarifiers work.

One thing to bear in mind is that because UV clarifiers are so effective, your filter may quickly become clogged with dead algae and will require regular cleaning. A small price to pay for an algae-free existence.

There is no need to remove any fish from the pond during the process as UV light does not negatively affect them. UV light does affect harmful bacteria and can even damage and destroy virus organisms, making the water safer for fish to live and swim in. During summer months, there is no problem leaving the UV clarifier running all day long to keep the algae levels down.

UV pond clarifiers, therefore, offer tremendous benefits to fish pond owners with algae problems – not only can you get rid of the algae, but your fish will stand a better chance of living to a good age than without the use of a pond clarifier.

Pond clarifiers that use ultraviolet light are only effective against these green and blue-green types of free-swimming algae and will not remove or reduce algae like string algae or other larger varieties. This is due to the fact that string algae will not pass through the filter and will therefore not be touched by the UV light. Other methods must be used to reduce these kinds of algae.


  • Effectively removes green water algae and blue/green toxic algae
  • Safe for pond animals
  • Can destroy virus organisms
  • Improves water quality
  • Helps keep water clear


  • Does not reduce larger types of algae, like string algae
  • Must continually run

Pond Dyes

In what may seem like a contradiction to the use of UV pond clarifiers, pond dyes are designed to help block out the UV light from sunlight.

Why is this important? The UV light is used by algae as part of their growth method – the less UV light, the less chance of photosynthesis occurring, the less chance of algae growth. This is different from the way a UV clarifier works – pond dyes work as a set of sunglasses do, protecting your eyes from harmful UV rays. A UV pond clarifier is more akin to being thrown into the sun!

Also, unlike a UV pond light, pond dye is effective against all types of algae – even string algae!

Pond dye products are safe to use with fish and other pond life but will not remove a large algae bloom. They are more suited to managing the pond once the majority of the algae has been removed by another method, or for keeping small blooms from growing further. Once a pond has been clarified by a UV light as much as possible, it is quite simple to keep algae from returning by the regular use of pond dyes.

Another benefit of pond dye is the benefit that they were originally designed for – to make your pond look beautiful!

Here’s a video explaining how to use this product and the different colors available.

Keep in mind, blocking ultraviolet light underwater will have an adverse effect on all underwater plant life, slowing the process of photosynthesis significantly.

Therefore, it is best to use when any plants have grown to a large enough size to be able to sustain themselves and provide their required benefits to the pond ecosystem.


  • Effective and long-term control against all algae, including green water and string algae
  • Safe for all pond life
  • Makes pond look more attractive


  • More used for control, than treatment
  • May have an adverse effect on underwater plant life

Chemical Algaecides

The use of algaecide products in a pond or lake can be a risky business as not all chemicals are conducive to the good health of fish (or other organisms).

In fact, if you’ve kept koi or other pond fish for a while, you’ll be aware that many factors can cause problems for their wellbeing.

Adding algaecide products to pond water that contains fish should be considered a last resort, and only really necessary under extreme conditions of algae infestation.

Pond algaecides work by attacking the algae cells and destroying the cell wall. This effectively kills and destroys the algae and makes such algaecides a highly effective remedy to the problem of algae.

Algae blooms can be destroyed within hours or days but that can come with a price. Although algae will cause many problems, rapidly removing it will also rapidly change the environment that your fish are living in. While the chemicals themselves may pose no direct threat to any fish – many algaecides are purported to be fish-friendly – the sudden change could be deadly.

The O2 levels in the pond will become lower as the algae die off, and the dead algae will sink to the bottom of the pond. These dead algae will now begin to decompose. The decomposition process requires – you guessed it – oxygen, further lowering the levels in the pond.

If you only have one or two fish, that will probably be fine. If you have a large quantity or the water is low on oxygen due to other factors, to begin with, your fish are going to struggle to survive as there will not be enough oxygen to support them.

Methods of oxygenation may be employed to increase the levels of oxygen in the water, including pumps, fountains, a waterfall, and pond spitters. However, if you are at all unsure about the oxygen levels in your pond or think that you may have too many fish to support a drop in the levels, avoid this type of pond algae killer at all costs. There are other methods of removing algae that will ensure that your fish remain alive and well.

Any plants you have in the pond should remain unaffected by algaecide treatments (unless the treatment is poured directly onto them) and will recover quickly as the environment changes.


  • Very effective at eliminating all pond algae, including green water and string algae
  • Cost-effective treatment


  • Some algaecide products may be dangerous to the pond environment, including any fish and plants
  • Can cause oxygen depletion in the water, requiring the use of a pond aerator

How to Get Rid of Algae in Pond Naturally

If you’re averse to using any sort of chemical or product that you might not typically find in a pond ecosystem, then here are several more natural alternatives to removing algae from your pond.

Manual Algae Removal

Manually removing the algae by hand or with tools (a rake, for example) is easy, fast, and arguably one of the most common algae control methods. It’s not the most pleasant of tasks but does get fast results and is one of the safest algae control methods you can use.

With this technique, you won’t be able to remove 100% of all algae in your pond, but will at the very least be able to improve the appearance of the water and reduce the amount of algae present.

It is not necessary to do this with your bare hands, of course, but if you choose to do so, then gloves for protection are advised. With the ability to grip, this is an effective method for removing string algae.

Certain tools like a pond rake may also come in handy when trying to remove string algae from the surface of your pond. Especially, if you have a larger pond or lake and can’t reach the middle with your arms.

If it still sounds like a little too much hard work, an alternative is to use a pond vacuum.

These devices will suck up anything you throw at them, including string algae, blanketweed, sludge, and more. They are more effective, quicker to use, and make the job much easier than pond rakes, but do cost significantly more – it’s a matter of balancing your budget against the amount of work you want to put in.

With larger ponds, they can be extremely effective, but if you are only dealing with a small pond you probably don’t need to run to the expense.

Solely using a manual removal technique will not result in a perfect pond. That said, removing the algae and then tackling the factors that cause algae growth in the first place (e.g. making sure there are no excess nutrients entering the pond) you’ll be on track for a much healthier pond.


  • Great way to remove larger algae, like string algae
  • Immediate results
  • One of the safest methods to control pond algae
  • No worry of dead algae clogging up filters


  • Not ideal for large ponds
  • Equipment and tools can be pricey
  • Not really effective for green water algae

More (Good) Algae

Just as there are good bacteria and bad bacteria, good algae also exist. Good algae require the same conditions for growth as bad algae, and so the presence of good algae will inhibit the number of the bad as they will compete for nutrients.

Well-established good algae will effectively shut out and control bad algae growth.

Commercially available treatments work by introducing a particular type of algae to your pond. They grow at the same rate as any other algae but are often chosen to be able to use photosynthesis earlier in the day than bad pond algae.

This limits the amount of pond nutrients available for the bad algae to consume , gradually starving it and preventing any further growth. Eventually, all of the bad algae are gone and are replaced by the good algae.

You might think that this just replaces one type of algae with another, but there is a benefit. There are microscopic organisms living in your pond water called zooplankton. While they are not too keen on the bad algae, they are quite happy to eat the good algae which are called diatoms.

As they are well fed, their numbers will increase while at the same time preventing your pond from becoming overgrown with the good algae. Fish like Koi and Goldfish will eat the extra zooplankton, keeping everything in balance.

Here’s a video explaining the process from the recommended Nualgi Ponds.

This is a safe and effective treatment for pond algae control but does not work instantly. Time must be allowed for the good algae to grow and thrive, and so if you’re looking for instant results you may be disappointed.

On the upside, it doesn’t involve the use of harsh chemical products and is normally effective within a few weeks. If you can wait that amount of time, it is a good product to choose.


  • Effective for smaller green algae
  • Safe for pond life
  • Good for the ponds ecosystem and water quality


  • Takes time to see results
  • The dead algae may clog up filters
  • Might not work on larger algae blooms

Barley Straw

Barley straw doesn’t kill or remove existing algae but can help prevent and control new algae growth. As the straw decays it will de-oxygenate the water, and so should be used with care if fish are in the pond – the fish will need oxygen to survive.

The decay of the straw is what helps keep the algae under control. After a few weeks of rotting, humic acid is produced. This reacts with the surrounding water, along with sunlight and oxygen, and produces a small amount of hydrogen peroxide. This is how the water becomes de-oxygenated, by the binding of oxygen into new compounds. With a high enough water-to-fish ratio, you should not experience any problems.

The amount of hydrogen peroxide produced is usually low enough to ensure the safety of fish but is high enough to control the growth of algae.


  • Prevents future algae growth
  • Effectively control algae for about 6 months


  • Overdosing ponds with barley can cause fish kills
  • May start to smell if it gets old

Pond Plants

Pond plants will not instantly get rid of existing algae blooms and are not a quick fix by any stretch of the imagination.

However, a well-planted pond will have fewer algae, as well as, less potential for growth. Aquatic plants require the same conditions as algae to grow – sunlight and nutrients. The plants in your pond will compete with the algae for these growth-essentials and give the added benefit of releasing oxygen into the pond during night time.

This means that your pond water will remain well-oxygenated which is beneficial to any fish you are keeping.

Some pond plants may be difficult for beginners to look after, but aquatic plants like the Hardy Water Lily and Hornwort are relatively straightforward and provide a good basis to build from.


  • Plants compete with algae for nutrients
  • Oxygenate pond water
  • Good for the ponds ecosystem and water quality
  • Help partially cover the surface area of your pond which blocks sunlight from feeding algae growth


  • Will not remove algae bloom
  • An extremely long-term algae control
  • Most plants require care

Pond Snails

Certain pond snails, like the Japanese Trapdoor Snail, like to feed on algae and vegetation.

These algae eating snails are good to have around if you have algae present in your pond. But, keep in mind, if you have more snails than there is algae to eat, they will find other food sources and may start feeding on any pond plants you have. And this can be hard to control, as snails can reproduce very quickly.


  • Natural way to get rid of algae
  • Good for a ponds ecosystem


  • Pond snails can reproduce quickly creating an overabundance
  • Takes time to see results
  • Snails may eat plants that you want around if there are not enough algae

How to Get Rid of Algae in a Farm Pond

Farm ponds are often larger than domestic ponds and may require stronger treatments or larger quantities for that reason alone.

Pond dye products and chemical treatments are effective solutions for removing algae blooms from large ponds. And, of course, having a good amount of oxygenating pond plants is an effective means of farm pond algae control.

Farms are a hotbed of nutrients and so keeping fertilizer, animals, and animal feed as far away from the pond as possible will help to control algae.

Should I Remove Algae From My Pond?

The short answer is that you can’t actually remove all the algae from your pond. No matter how hard you try, there will always be a tiny number of algae in any given pond, and the fact of the matter is, that’s fine.

When that tiny amount increases, it starts to affect how the water looks, as well as interfering with the ecosystem that already exists. As algae use nutrients and oxygen to help with growth, there will be a reduction of the availability of these things in the pond as the bloom progresses.

If you have fish or other aquatic life in your pond, they will require their fair share of these things to survive. A reduction could have an adverse effect on the wellbeing of all the animals in your pond, and so it is wise to keep a check on the amount of algae present in your pond.

As algae die, they will sink to the bottom of the pond and cause a sludge (as well as reducing oxygen levels even further). This will again affect the fish as well as the clarity of the water and may also affect any plants you have in the pond.

Further, you may begin to notice a rather unpleasant smell as time progresses.

Without fish or plants, you may decide to put up with the unsightly growths and strange smells. However, if you want your pond to thrive in the best way possible, it’s a good idea to get rid of the algae as soon as possible. The longer you leave it, the more chance it has to build up, and the harder the task becomes to remove it.

What Causes Pond Algae Growth?

Before trying to rid your pond of algae, you should understand what caused the growth.

Why? If you try to control algae in your pond without knowing what caused it in the first place, it will most likely come back.

First of all, algae are present in all forms of water, even water treated at your local water company.

Did you know…

Adding fresh tap water to your pond may cause the growth of algae, as a single alga or spore can start what is known as an algae bloom – the growth that you can see in your pond water.

Once your pond water is affected with algae, it will need nutrients to develop and grow.

These nutrients can come from a number of sources, including:

Fish Waste

One of the biggest sources can be waste produced by fish, especially large pond fish like Koi. High-quality fish food will help to alleviate this problem, as lower quality fish food often contain filler ingredients that the fish cannot process. This leads to excess waste production.


Other sources of nutrients may include leakage into the pond from external sources. If there is a hole or tear in the pond lining, fertilizers or other nutrients may enter the pond from the surrounding area (check out our guide on how to find pond leaks and quickly repair them).

Further, the use of sprays to help plant growth near the pond may also result in airborne particles entering the water – and if it is good enough to make a plant grow, it will be able to help algae grow.

New Ponds

Established ponds will contain “good” bacteria that require nutrients to survive. This beneficial bacteria will cause no problems for humans or animals and are beneficial to the lifecycle of the pond. And importantly, it will consume nutrients that otherwise would be consumed by algae!

Unfortunately, new ponds will not have this benefit. Fresh, “clean” water will fill the pond and potentially contain algae or spores, and no beneficial bacteria will be present in the clean water to fight against it.

The clear water of the new pond will aid in photosynthesis allowing the algae to grow and reproduce more quickly, while there will also be no beneficial bacteria around that can help to break down and remove dead algae.

Removing algae

Nothing is more bothersome than an excess of algae in a pond. You want to remove them. A pond is an unbroken ecosystem. Biological wastes are converted by bacteria into nutrients for water plants, which in turn give off oxygen to water, thus providing a healthy pond environment. Even if a pond has been fit up properly, problems may arise, which can upset the biological equilibrium, resulting in objectionable algal growth.

There are different kinds of algae which occur in ponds:

  • Beard algae
  • Blue-green algae
  • Brown algae
  • Fibrous algae
  • Floating algae

How the algae problem is caused?

Algal growth always forms owing to the fact that the water plants present are not able to completely remove nutrients from a pond. A surplus of nutrients is arising of which algae are taking advantage.
Little algal particles are always latently present and will develop as lightning. As opposed to plants algae make only low demands on the quality of water. Consequently algae are growing more quickly under circumstances where water plants can not yet develop well. Especially in newly built ponds the growth of important oxygen producing plants will stagnate owing to floating algae.
Algae will make a green mass of the pond water and spoil pond fun and restrict plant growth.

Prevent algae

We have some tips for you to fight the formation of algae:

  • Set more pond plants.
  • Remove dirt from the bottom and clean the filter.
  • Do not feed the fish too much. Take care that the fish will eat the feed distributed within a few minutes.
  • Regularly remove fibrous algae as much as possible from the pond.
  • Inspect the quality of the pond water and adjust water values if necessary.
  • Apply substrate on the bottom of the pond. This is important for the development of micro-organisms.

Fighting algae

The first step to an algae-free pond is to test the water. On basis of the result a diagnosis can be made and a plan to remove algae. The most important values can be determined using a pond test set: pH , GH and CH value.

For the pond environment in particular the pH value is important, because it gives us information about the CO2 content of the water. If in the morning the pH value is relatively low (pH 7-8) and measured in the evening relatively high (pH 8-9) pond environment is functioning, plants will be growing well. Whereas the water will be clear. Measures taken to raise the pH value to a more favourable level in the long term should be based on activating the micro-organisms by applying bottom substrate and bacteria and on setting pond plants, which for their supplying of CO2 will not have to rely on water (floating) plants, water lilies and marsh plant). The use of peat granulate can expedite the decrease in the pH value. A too low pH value (pH 6 and lower) indicates that the environment is acidifying and it is a threat to all pond inhabitants. Especially in winter too low pH values may occur under certain circumstances.

The joint hardness of the water is determined by calcium and magnesium. This is called the GH value of the water. A proper GH value for pond water ranges between 8° and 12° GH.
Most kinds of pond plants will optimally grow within these values, whereas in this medium hard water the development and the activity of the micro-organisms are optimum.

The carbonate hardness (CH value) is an important pillar in pond environment. The CH value is also referred to as temporarily hardness, whereas it is also referred to as the acid binding capacity.
Carbonate is formed by binding free carbon dioxide (CO2) to calcium and or magnesium. Thus it forms a carbon dioxide (CO2) source for water plants and algae. A proper CH value ranges between 6° and 10° GH.

If the pH, GH and CH values should deviate, they will have to be adjusted. Special means are available to realize this.

Remove algae quickly

The measures referred to here aim at reducing the growth of fibrous algae by biological means and finally to stop it. The whole process will take a number of months. This period can be reduced by applying a course of treatment with an algae fighting product. Please bear in mind, however, that this kind of product fights the symptom algae but that it does not remove the cause.

Equipment has been developed to solve the algae problem in garden ponds definitively. They function according to the mineralization principle. By mineralization the growth of fibrous and slimy algae is rendered impossible, whereas water plant growth is stimulated.

A lasting solution for the floating algae problem (green water) is a UV-C Filter. The ultraviolet radiation will kill floating algae, germs and moulds.

A filter equipment is also a relief for the algae problem. One the one side the water is kept
clear by filtrating the water, On the other water circulation will provide sufficient oxygen. A filter equipment will filter the pond water both mechanically and biologically. Mechanical filtration is based on the principle of removing organic and inorganic dirt particles as well as colourings. The principle of biological filtration is to obtain a better and quicker conversion of organic particles by means of micro-organisms. An integrated biological filter will enhance the activity micro life and thus it stimulates plant growth.

There are many kinds of filters; floating filters, pressure filters, multi chamber filters and flow filters.


Some Algae is essential for a healthy ecologically balanced pond….

Algae is not only a normal part of any pond but also a beneficial one. It is a food source for many aquatic animals, however it can also be the bane of nearly all pond owners.

Algae is the food source for tadpoles, so if you are trying to create a habitat for frogs, you need some algae.

Careful monitoring and management are the keys to most successful ponds, however there are ways to make life easier. A well designed pond can reduce the algae problems, by not creating an environment where the algae can flourish.

A basic understanding algae helps us avoid algae problems.

Algae problems are easier to manage if we understand, that like any plant, algae needs food and light to grow. By designing and constructing your water garden so that you reduce light and nutrient availability, combined with some regular maintenance, algae control is far easier to achieve.

What are some of the factors that increase the risk of algae problems?

  • High light levels. Algae like any plant, needs light to photosynthesise and grow.

  • High water temperatures stimulate faster growth.

  • Over stocking of fish, leads to more fish waste. More fish waste leads to higher nutrient levels in the pond water.
  • Excess nutrients is a major cause of algae problems.
  • Pollutants in the pond water can be the source of many problems for aquatic life. They may be chemicals or excess soil particles from the garden, others may come from the runoff water, that collects from gutters and drains before ending up in the pond. Some may become harmful or even toxic, leading to an unbalanced pond ecology. Some aquatic life may die, while others may run rampant due to the reduced competition.
  • Poor water circulation. Most algae grow better in still water or stagnant pond conditions.
  • High pH or alkaline water increases the risk of algal blooms. This is more common in ponds that are constructed from concrete, where the lime in the cement often leaches out. Care should also be taken in the careful use of certain types of rocks in your water features. For example, sand stone and some types of honey comb rocks may also increase the pH in the pond water.

Good pond design is the best way to prevent algae problems

Prevention is always better than the cure. Good pond design helps us to minimize algae problems and reduce the need for a pond algae treatment.

The 2 main factors that need to be addressed are light and food.


Light needs to penetrate the pond water for the algae to grow. Shade from trees, walls and especially other aquatic plants, all help to reduce the light entering the pond water and therefore the ability of the algae to grow.

Designing the pond side walls as steep and as deep as possible, helps to increase the pond volume relative to the pond’s surface area. This creates a more stable pond environment as the larger volume takes longer to warm up. Remembering that warmer water speeds up algae growth.

Colouring the inside of the pond as dark as possible also helps to reduce the light reflection.


The build up of excess leaves, that decompose in the bottom of the pond, can be the source of many nutrients. Regular pond maintenance, to remove the leaves, helps to minimise the excess nutrients.

Adding more aquatic plants. Aquatic plants consume the same nutrients as algae, so by increasing the amount of plants you effectively reduce the amount of food available for the algae.

Adding fish or other pond animals, increases the nutrient load due to the increase in their waste.

Overfeeding the fish or other aquatic life, leads to increased waste through uneaten food settling to the bottom of the pond and then decomposing to release more nutrients into the pond water. Only feed the fish what they can eat with in a minute or two. During Winter it is often best not to feed at all.

Over fertilizing the aquatic plants can increase algae growth, as they feed on the same nutrients as the plants.

Incorrect fertliser or fertiliser application. Slow release fertilizer should only be added to the plant’s root system. Slow release fertilizer tablets inserted into the soil are one of the safest methods of fertilizing pond plants. Liquid fertlisers should not be used.

Adding beneficial bacterial cultures helps consume nutrients and organic waste. These recyclers help to reduce the available nutrients and so reduce the potential algae growth.

Biological filters create an environment where the beneficial bacteria can grow and help to reduce the nutrients in the pond water. This is often required in fish ponds as the increased waste can lead to increased levels of toxic ammonia. The biological filters help to consume the waste and detoxicify the pond water.

Frequent, partial water changes help most water gardens. They are the best way of diluting nutrients.

What are the best algae control methods?

In order of importance we can classify algae control into 3 groups.

1. Biological algae control.

Biological algae control is essentially through competition. This may be through the addition of aquatic plants that compete with the algae for light and food. What would you rather have? More plants or more algae?

Beneficial bacterial cultures should be added to the pond water. Some of these cultures help to decompose the organic matter, such as leaves and fish waste, while others consume the nutrients that the algae feed on.

2. Mechanical algae removal.

Most particulate or screen filtration systems don’t really trap and remove algae very well. String algae removal is often difficult through the fact that it easily clogs up the screens and plumbing. These mechanical type filters do filter out sediment, which may be a food source for some algae.

Some blanket or string algae removal can be achieved manually, through scooping with your hands, or using various tools such as sieves , nets and screens to scoop them up. Sometimes a stick may be the simplest tool. Just twirl the stick around and you’ll find that the algae starts to wind up on to the stick.

3. Chemical pond algae treatment.

There are a vast number of pond algae treatment products available on the market. Some are Copper based and rely on the fact that algae is sensitive to the copper at relatively low concentrations. Care needs to be taken, as repeated doses or high concentrations can lead to other plants dying due to the increasing toxicity.

Other products contain chemical herbicides. These chemicals, like the copper based products, also affect the algae at relatively low concentrations. Similar precautions should be taken to avoid overuse and increasing toxicity.

Some chemical treatments do not actually harm the algae, but actually treat the pond conditions that may otherwise stimulate algae growth. In ponds with a high pH there are various chemicals that help to make the pond water more acidic. Activated Carbon products can also be added to the pond to absorb excess nutrients and so reduce the available food.

Balanced algae control

By introducing more plants into the pond you create more competition for both the available sunlight and also the amount of freely available nutrients in the water.

When you include fish into your pond you tend to increase the amount of biomass (organic waste) and hence the amount of nutrients increases.

In most small ponds the plants cannot be the only source of control. Filtration systems should be included in the pond design. Biological filters help to control the nutrients in the pond and UV light filters can also be introduced to assist in the control of green water algae.

Through the monitoring of pH, carbonate hard water, ammonia toxicity, high levels of nitrates and nitrites we can determine the best course of action to help create a more stable pond environment which then reduces the risk of algal outbreaks.

Frequent, partial water changes between 10 and 25% will help most ponds. They are the best way of diluting nutrients and toxins in the pond water.


  1. Follow the links for further information on filtration, pond treatments or pond maintenance

Leave a Reply

Your email address will not be published. Required fields are marked *