This is why your farm pond water turns green or brown

A farm pond is a small tank or reservoir-like construction that some people have constructed on their property. The purpose of a farm pond is to store surface runoff generated in the area. It can also be helpful for those living on farms by acting as a water supply for irrigation, cattle feed, and fish production. Farm ponds must be maintained to remain useful. Green or brownish colored water can indicate issues that need to be addressed to improve your pond’s health.

Why is your farm pond water turning green or brown? Farm pond water can turn brown because of plant tannin, certain wildlife, soil erosion, and the build-up of sludge. If your pond is turning green, it’s most likely caused by a build-up of algae. 

In this article, you’ll learn why your farm pond water is turning green or brown, how to get your water clear again, and other tips for farm pond maintenance.

What Causes Pond Water to Turn Brown?

Brown farm pond water is not a rare occurrence. According to the blog, “What to Do When Your Pond Water Turns Brown,” from Fitz’s Fish Ponds, there are several reasons it can happen. 

Four major things that can cause your farm pond water to turn brown are:

  • Tannin 
  • Wildlife
  • Soil erosion
  • Sludge


Farm pond water can turn brown because of molecules called tannin. Tannins are polyphenolic and derived from plants, especially plant types that break down. Many plants create tannin, and it’s even used as an ingredient in western tea to give it its brown color. It’s also used in some wines and coffee for brown coloring.

Tannin helps protect plants from predators, and it helps them grow. Without tannin, many plants wouldn’t be able to survive, but you don’t need it gathering in your pond water. The more tannin that builds up in your water, the browner the pond will become.

Wildlife’s blog, “Why Does Pond Water Turn Brown?” explains that certain wildlife is a major cause of pond water turning brown. There are fish called nuisance fish that contribute to the brown color. Some types of nuisance fish are goldfish, carp, and bullhead. 

They’re called nuisance fish because they spawn and feed in shallow water. This causes the mud to get kicked up from the ground and get mixed in with the water. As a result, if there are too many living in your farm pond, the water will turn brown and appear muddy.

Furthermore, ducks and geese can be major problems for farm ponds. They like to feed on bank vegetation, which increases erosion and muddies the water.

Soil Erosion

Soil erosion is another issue for anyone that doesn’t keep up with maintenance around their farm pond. The eroding soil along the banks of your pond can cause soil particles to get into the water. If this doesn’t happen often, it isn’t too much of an issue. However, if this happens consistently, over time, the particles will muddy the water and turn it brown. At this point, it can be very difficult to get the water clear again.

Clay particles are especially problematic. With mud, the particles are attracted to each other and clump together, making it manageable and easy to clean. However, clay particles repel each other instead of clumping together, so it spreads throughout the entire pond. As a result, the water will start to look brown and soupy.


Aquanooga describes pond sludge as “an accumulation of organic debris that settles in the pond bottom. Most commonly the sludge will be a mixture of leaves, fish waste, decaying plant debris, dead algae, and debris washed into the pond with rain run off.” A small amount of sludge isn’t a big issue and is unavoidable. Every farm pond (or any body of water, for that matter) will have a small amount of sludge. 

However, if there is too much sludge, it can turn water brown. If it isn’t kept under control, it will create a seal that prevents oxygen from circulating. Once this happens, it can be very difficult to get back under control.

How to Get Rid of Brown Water in Your Farm Pond

When you look out at your farm pond and see that it’s turned brown, you’ll want to change the color. Luckily, there are ways to remedy this situation. Pond Informer discusses how to clear your water in their article “The Best Clear Pond Water Treatments 2020 (Ways to Get Clear Pond Water).”

Three of the best methods for treating a pond with brown water are:

  • Using Polywool filter media
  • Using activated carbon treatment
  • Water change and treatment

Using Polywool Filter Media

If you determine that your pond water is turning brown because of tannin, the easiest way to deal with it is to use a highly absorbent and fine filter media material called Polywool. This material will directly absorb tannin, and it will also catch other finer debris that may be contributing to the unfortunate color of your pond water. 

Most mechanical filter media isn’t fine enough to catch such small particles, so you need to use Polywool, or it won’t work as effectively.

You can use Polywool by adding it directly to your filter box. However, once you add it, make sure to monitor the pressure buildup carefully. Since the material is so fine, it can greatly reduce the flow of water and build pressure inside your filtration system. If you’re having problems with pressure building up, you can add it directly under the filter outtake hose, under a waterfall, or in a fountain.

You will need to change the material once it becomes clogged until you reach the water clarity you desire. Depending on the severity of your situation, this could take a few days or even a week in some cases. When you apply the Polywool, you should start with a thickness of 12 to 15mm and slowly increase the thickness as the water clarity improves.

Using Activated Carbon Treatment

The next method you can consider is using activated carbon treatment. This method will remove all harsh pollutants that your filter can’t remove on its own. This includes chemicals such as pesticides, chlorine, perfumes, and tannins.

You can combine activated carbon with a Polywool media filter to get the best results. However, it is typically placed in a mesh filter bag inside your filter box. As water passes through your filter box and mesh bag and touches the surface of the carbon, the chemicals and tannins will be eliminated. 

When the chemicals are eliminated, they will stick to the outside of the carbon. As a result, you will need to replace the carbon regularly until all the tannin is removed and you reach the desired water clarity. 

Ideally, you will purchase activated carbon with a large surface area. This makes it more efficient in eliminating unwanted chemicals, and it also reduces the frequency that you need to change it.

Water Change and Treatment

Finally, if neither of the above methods work, you might need to consider performing a water change. This method should only be used as a final measure if nothing else works. It’s not recommended that you do this unless it’s necessary because a water change will greatly reduce the beneficial bacteria populations in your farm pond. 

However, if you do choose to go through with the water change, you should make sure to use a dechlorinator afterward. This will remove any residual chlorine that can harm fish and kill pond bacteria. Additionally, they’re safe for the fish and plants that live in the pond, and they’re great for eliminating tap water.

What Causes Farm Pond Water to Turn Green?

As opposed to brown water, where there are several major causes, there is only one major cause of your farm pond water turning green, and that cause is algae. Algae grow in farm pond water when there is a nutrient imbalance in the pond. The Pond Experts explain that there are several reasons that your nitrate and phosphate levels can become elevated and disrupt the balance in your farm pond in their article, “How to Clear Green Pond Water (Algae).” 

Reasons that a nutrient imbalance can form in your pond include:

  • Sludge accumulation
  • Too many fish
  • Not enough plants

The first major cause of these chemical levels getting elevated is sludge on the bottom of the pond. When organic material, such as dead algae or fish waste, resting on the bottom of the pond decomposes, nutrients are released into the water. Nutrients are food for algae to grow. So, whenever something is decomposing, the algae in your farm pond is being fed. As more sludge builds up at the bottom of your pond, more nutrients are released.

You can also get an excess of algae from having too many fish in your pond. Although you may think having koi or goldfish in your pond gives it a little extra life, they’re contributing to the algae problem. This is because if you have too many fish, they’ll produce more waste, which gets broken down into nitrates and allows algae to grow.

Koi can be dangerous in this regard because people buy them when they aren’t fully grown, and they don’t realize how big they can get. Since they grow to over a foot in length, having four or five in an average-sized farm pond can cause a nutrient imbalance. 

Goldfish don’t grow to be very big, but they breed very quickly. They will spawn several times a year, so their population can get out of control fast. You should note that it only takes a season or two for several generations of goldfish to pass.

Finally, if you don’t have enough plants in your water, algae will get out of control. This is because regular plants compete with algae for nutrients and food. Since they consume many of the same nutrients that algae do, having plants can prevent algae from getting out of control. 

How to Eliminate Green Water in Your Farm Pond

Eliminating algae and clearing the water in your farm pond isn’t easy. However, with the right tools and information, you’ll have your pond back to normal in no time. 

There are three major actions you can take to eliminate algae from your farm pond:

  • Clean your pond and reduce sludge
  • Reduce fish load
  • Add more plants

Clean Your Pond and Reduce Sludge

The first thing you should do is clean your pond and reduce the sludge. The number of nutrients in your farm pond that feed algae can be greatly reduced by cleaning the sludge that exists on the bottom of your pond. 

There are many ways that you can do this:

  • For smaller ponds, use a long-handled net to remove most of the sludge. 
  • For larger ponds, use a pond vacuum to remove as much sludge as possible. To keep sludge levels at a manageable level, you should do this a few times a season.
  • Cover your pond with a net in the fall to prevent leaves from getting in your pond in the first place. This will make maintenance easier and reduce the frequency you need to clean the pond later in the year. 
  • Add a sludge and muck reducer to the pond to reduce organic matter. Muck reducers are made of natural, beneficial bacteria and enzymes that consume sludge. They then convert the sludge into nitrogen gas that will bubble out of the pond.
  • Use a pond skimmer if you have a larger pond to clean the bottom of the pond. They run along the surface of your pond and prevent debris like leaves or grass from sinking to the bottom. Having a pond skimmer also makes filter and pump maintenance much easier. For example, you can use this TetraPond Skimmer (available from Amazon). It’s great for ponds up to 1000 gallons, and you can use it with pumps that range from 550 to 1900 gallons per hour. It will help protect your pump from clogging while keeping the surface of the pond clean. As a plus, it ships in certified frustration-free packaging. 
  • Use bottom drains to continuously pull waste from the bottom of your pond into the filtration system, where it can be removed with ease. Having a bottom drain almost eliminates the need to vacuum the bottom of your pond manually.
  • Use Nualgi. When you add it to your pond, it will create a bloom of Diatom algae. These algae out-compete the algae that infest your pond and turn it green. As a result, bad algae will die off because the Diatom algae are taking all its food.

Reduce Fish Load

Fish can be a major problem for any farm pond owner. If they get to be too big of a problem, you might be forced to reduce the fish population in your pond. It’s easy to get attached to koi and goldfish that have been around for a long time. However, if you don’t remove most of them, you’ll never have clear water again. 

There’s also the risk that having too many fish can ruin the water quality and get the fish sick, which can lead to sudden die-offs in the winter. Try giving some fish away to your neighbors or friends that have ponds like yours. You can also sell many of your fish or give them away by putting up ads in the newspaper.

After you go through the difficult process of removing most of the fish from your pond, resist the urge to purchase more. With the remaining fish, do what you can to feed them less. Most ponds have an abundance of natural food that fish will eat, so you don’t need to feed them often yourself. They will stay healthy without being fed often by you, and they won’t reproduce as often or in as massive quantities.

Add More Plants

Finally, even if you do the above methods, you should add more plants to your pond. This is the best way to keep your algae situation under control in the long term. It’s also the most natural method of reducing algae, so there’s no risk of causing unwanted damage to the ecosystem.

Plants compete with algae for food. So, if you have enough plants, you won’t get many algae. The only thing you need to be careful of is adding foreign plants. Foreign plants could bring chemicals that could harm or damage other wildlife in the area. Make sure that you are only using plants that are native to your area.

Managing Your Discolored Farm Pond Water Problem

For those of you that have a farm pond, you know how much it adds to the aesthetic of your property. However, it only looks good if you take care of it and maintain the color of the water. If your farm pond turns brown or green, it won’t look good at all. Make sure you’re committed to the maintenance of your pond. You need to have a good filtration system to prevent debris from getting into the pond. Additionally, make sure that you have enough plants in the pond and that your fish population stays under control.

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