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How To Use Activated Carbon In Your Pond (With Best Carbon Buying Guide)

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

Filtering chemicals with the help of activated carbon has seen a rise in popularity in the past years.

This has been specially popular for ponds with fish and other aquatic animals.

Activated carbon can naturally remove any large amount of chemicals and organic pollutants.

This clears and purifies the water, making it cleaner and a much better habitat for fish and water plants.

In this article, we take a look at the benefits of activated carbon and how to use it.

We also found some of the best carbon products suitable for every pond size.

What Is Activated Carbon?

What Is Activated Carbon?

Also known as activated charcoal, activated carbon is a black-looking material which resembles your typical charcoal.

It is used commonly used for chemical filtration of the water in your pond.

This means that it filters out any harmful chemicals in your pond which cannot normally be removed through other means, such as biological filtration.

Activated charcoal can remove a range of different chemicals and substances, including chlorine, perfumes, insecticides, pesticides and odors.

It can also easily remove any organic pollutants such as tannins, residue algaecide or excess fish pheromones.

All these things would be difficult to be filtered with normal filtration methods. However, they can be filtered out of the water with activated carbon.

For example, when leaves drop on your pond you can remove them with a net, but these natural debris leave tannins (organic color) behind.

This cannot be easily removed with a net or other biological filters.

But activated carbon is not just suitable for filtering tiny, organic particles but it can also be used for neutralizing chlorine.

This is especially useful when you fill up your pond with water that comes from a chlorine-heavy water source.

Also fish stocked ponds can benefit from filtered water through activated carbon. It removes any pheromones produced by koi carp or other fish. 

This will neutralize the water and balance the pH to a healthy level for aquatic wildlife.

How Does Activated Carbon Work In Your Pond?

Activated charcoal is a type of carbon which has very small pores, which can increase when coming into contact with another substance. 

This means that when activated carbon comes in contact with chemicals or other substances, it can quickly absorb and neutralize these organic and inorganic substances.

The chemical or substance sticks to the surface of the carbon itself. Then, the activated carbon slowly creates a thin layer of adsorbate material around the carbon.

This film will eventually cover the carbon and it will need to be replaced.

We found that the best activated charcoal is highly porous, which means that it has the largest surface area to attract more of the chemicals.

The greater the surface area of your carbon, the more of the chemicals and substances can come into contact with it.

This means that the more porous your activated carbon, the more of the chemicals or substances you will be able to neutralize.

It’s important to note here that this process does not affect the balance of the water. The activated carbon doesn’t release any substances into the water.

This makes activated carbon the most natural filtration option for garden ponds as well as swimming ponds.

When Should You Use Activated Carbon In Your Pond?

When Should You Use Activated Carbon In Your Pond?

You can use activated carbon for your pond whenever you want to neutralize chemicals or excessive pollutants in the water of the pond.

As activated carbon is an excellent neutralizing agent, it should not be used when you are treating your fish for any health issues.

Activated carbon removes any medicine or water treatment particles from the water. This can affect the effectiveness of the treatment for the fish.

The same applies to pond water dye products and algaecides. Activated carbon will filter these chemicals from the water.

Due to its high effectiveness, activated charcoal should be used only after a course of medicine, and when you are done treating water dye or algaecide.

Once you have finished with these treatments, you can apply activated carbon.

This way, it will not interfere with any chemicals that you intentionally use to support the health of your fish or the rest of the pond.

If you do not currently treat your garden pond with any organic material or chemical substances, then you can use activated carbon at any time, such as when you notice a discoloration of the water.

You can also use activated carbon as part of your pond maintenance.

Benefits Of Activated Carbon For Ponds

We have touched on some of the benefits of activated carbon above, but let’s take a look at the great advantages of activated charcoal in more detail.

Keeps Your Pond Water Clean And Clear

Whenever we talk to someone about activated carbon in their ponds, we find that the greatest benefit of this neutralizer is how it keeps the water clean and clear.

Activated carbon removes any tannins that could discolor the pond water. Tannin is a natural coloration particle that occurs in pollen, leaves and grass. 

These things often naturally find a way into your pond turning the water a shade of brown or grown.

As the particles are so small, they are almost impossible to remove without any help.

And tannins do not only make the pond water look unsightly, but they also create an imbalance in the water, causing harm to fish and other aquatic organisms in your pond.

With activated carbon, you do not need to remove the pond water or anything else.

You just add it to your pond, and it neutralizes the tannins quickly and effectively.

Removes Harmful Chemicals And Substances

There could be any number of harmful substances and chemicals that end up in your garden pond (see also ‘How To Shade A Garden Pond (Heat Protection Guide)‘). 

Although the majority of these may be filtered through mechanical filter systems, some of the heavy organic chemicals can only be filtered out with the help of activated carbon.

For example, if you need to treat your pond fish with medicine, then activated charcoal can filter the residue of the medicine after the treatment course.

It can also remove any pesticides or insecticides that have ended up in the water.

These can come through the air, or they may have found their way in from surrounding grass or water sources.

Activated carbon can ensure that these pesticides do not wreak havoc in your pond.

In addition, it also neutralizes chlorine which may be in the water from your water source when you fill the pond with new water.

Improves Fish Health And Plant Grow

A lot of ponds contain fish and other aquatic wildlife that needs a balanced ecosystem to survive and thrive.

However, with the threat from pesticides and other chemicals, fish health can quickly be threatened.

But also the fish themselves produce a large amount of waste and fish pheromones that pollute the water.

An excessive amount of pheromones leads to a reduced growth rate in fish, and it can cut down the number of healthy fish in your pond. 

Simply add some activated carbon to your pond to neutralize the pheromones, and balance the pheromone levels in the water.

Reduces Odors And Smells

Ponds that are not healthy can quickly start to smell. This may be caused by an excess amount of sulfates which can cause your pond to smell like sewage.

An imbalance in the pond water does not only cause the water to smell but there is also more sludge (see also ‘Best Pond Sludge Remover‘) at the bottom which reduces the oxygen levels which fish and aquatic plants need to breathe.

Adding some activated charcoal to the pond water will act as a filter and slowly remove any of the organic substances that cause the bad smell.

Over time, this will also improve the balance in the water quality.

Substances That Activated Carbon Cannot Remove

Substances That Activated Carbon Cannot Remove

Although activated carbon is excellent in removing a large range of different substances, there are things that the carbon cannot remove.

Source Of Chemicals

Activated carbon is able to neutralize a large amount of different chemicals but it cannot remove the source of any chemicals coming into your pond.

You will need to find out what chemicals are present in the water of your pond, and then try to remedy the source.

If you do not stop the source, then the water will turn as soon as you remove the activated carbon again.

Algae Bloom And Green Water

When your pond water has turned green, then this is likely caused  by an overgrowth of algae.

If you add activated carbon, you may notice a small improvement but it won’t be able to stop the large algae growth.

In order to stop algae blooms, you will need to apply algaecide or a UV water clarifier (see also ‘Best UV Pond Clarifiers‘).

Our preference is always the more natural algae clarifier to ensure that your pond stays as organic as possible.

You can safely use activated charcoal together with the clarifier.

Pond Sludge 

Pond silt, or also known as pond sludge, is any decomposed organic material that gathers at the bottom of your pond.

This can be any kind of organic matter, including leaves and fish waste. This sinks to the bottom of the pond and decomposes further.

This decomposition releases harmful substances which can impact the water balance of your pond.

While activated carbon can help with removing some of the pond sludge, you will need to remove the sludge manually.

This can be done either with a pond vacuum cleaner or a sludge removal product.

Where To Buy Activated Carbon And How To Find The Best Products

You can pick up activated carbon from almost any good pond and aquatic retailer.

There is a large range of brands that offer activated carbon. They usually come in different packet sizes as well.

When you are looking for activated carbon, you need to check the maximum surface area and the purity of the product.

Make sure that the product contains only carbon with a large surface area which is suitable for the most effective chemical neutralization process.

We found this Carbon Pad from Amazon ideal for ponds of all sizes. This pad can be easily cut to the right size and added to your water filter. 

How To Use And Dose Activated Carbon

The right dose and how to use your activated charcoal depends on the type of product you have chosen, and also the amount of chemicals and substances in your water.

We recommend using a dose of around 4 to 6 pounds of activated carbon for every 1000 gallons of pond water.

This is the best starting point, but if you notice that your pond is particularly full of chemicals, then you may also increase the dose according to the recommended instructions by the manufacturer.

You should place the activated carbon in the area with the strongest water flow. The best place for this is the filter box, or under a waterfall (if you have one).

It’s important to note here that you should never put loose activated carbon into your pond.

It should also be inside a mesh filter bag. This will hold the carbon inside and still allow it to filter the water.

Depending on what product you opted for, and the size of your pond, you may need more than one carbon filter bag to ensure that all the substances and chemicals are properly filtered.

How Often Should You Replace Activated Carbon?

It’s always best to use the best quality activated carbon you can find. You will need to replace this only every 2 to 3 months.

You may notice that a pond with a lot of chemicals will need more frequent changes of the activated carbon.

If your pond is particularly dirty, then change the carbon filter bags every few weeks.

As part of your pond maintenance, you should leave activated carbon in your pond for a maximum of 4 months. 

If you leave the carbon for longer than that, chances are that the absorbed substances may enter the pond water again.


Activated carbon can be used in additional to the mechanical and biological filtration processes for a pond.

It is easy to use by just adding it to your filter box or as a filter bag in the water.

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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