Why is There Foam on My Koi Pond?

The most common reason foam appears in an ecosystem pond is organic debris breaking down in the water. This debris can come from lots of sources, including leaves, pine needles, fish waste, uneaten food and fish spawning.

Seeing foam in your pond skimmer is normal and usually not a cause for concern. If it’s in the skimmer it means the pond skimmer is doing a great job of pulling the debris out of the pond.  Large amounts of foam in the pond, though, can look unsightly and might be a symptom of other issues in your ecosystem.

At a Glance: What Causes Foam in a Pond? And How Do I Fix It?

  • White or brown foam is a natural result of organic material (leaves, fish waste, uneaten food, etc.) breaking down in the pond.
  • Foam is especially common during the spring fish spawning season.
  • Foam is not harmful to fish and is a normal part of the pond ecosystem.
  • Use Pond Foam Free to quickly reduce foam.
  • For a long-term fix, take steps to improve your filtration and reduce the nutrient load in the pond.

Why is My Pond Water Foaming?

Pond foam is nothing more than a mix of air, water and organic pond material.

In normal conditions, the surface tension of the water creates a barrier between the air and the pond’s surface, preventing bubbles. This barrier breaks down, though, as leaves, fish waste and other materials dissolve into surfactants: compounds that break down that surface tension (similar to bubbly dish soap in your sink). When something, like a waterfall, agitates this water, large amounts of air bubbles form and break through the weakened barrier to create foam.

Foam can form in any pond but is most likely to pop up in ones with fish. The more fish you have, the higher the nutrient load in the water – which means more bubbles.

Foam can form during any time of year but is especially common during the spring spawning season as fish release organics into the water. 

Is Pond Foam Dangerous for Fish?

fish spawn pond foamPond foam is usually a temporary problem that is usually harmless and will not hurt your fish.  The best course of action is often to just wait for it to disappear on its own.

Some conditions that lead to foam are actually a sign that your ecosystem is working properly. If you have a skimmer, for example, a small amount of foam inside means that it’s doing its job of pulling in debris (and foam) from the rest of the pond.

Fish spawning is another healthy cause of foam. As female fish release their eggs, and males rush to fertilize them, the pond fills up with protein-rich organics. Couple this increased organic load with increased fish behavior as the males encourage the female to release her eggs, and you have a perfect recipe for foam. Luckily, this foam will usually subside as the mating season closes.

On rare occasions, pond foam can be a sign that your pond has too much built up debris. If this is the case, you’ll typically also see other issues in your ecosystem, like chronically mucky water and poor fish health. If the pond has a lot of built up muck and debris, a thorough cleaning might be needed.  

Some water treatments can also cause foam in the pond. 

If you aren’t convinced that any of the above common reasons for foam in your koi pond, try testing your pond water. Start with checking for ammonia, nitrites and nitrates. These tests can usually determine if you have any more serious issues with your pond.  Stop by for a  free pond water test at Splash.

How Do You Get Rid of Foam in a Pond?

Small amount of foam in your pond are a normal, natural and expected part of your ecosystem. If the pond has a skimmer, you’ll often see a little bit in your basket as it pulls foam and debris off the surface of the water.

While the foam itself won’t hurt your fish or pond life, large amounts of it can be a symptom of too much organic material in the water. That means any long-term fixes for reducing foam need to involve reducing the pond’s bio-load.

How to Quickly Reduce Pond Foam

The best way to clear up pond foam is to reduce the amount of organic debris in the water and wait for the ecosystem to balance itself. But what do you do if you have a pond full of foam, and a backyard barbecue planned for tomorrow?

Pond Foam Free is a great tool for quickly breaking down bubbles. Simply add one pump of Foam Free per 100 gallons of pond water. This product is completely safe for fish, pets and the rest of your pond life.

Other options for removing foam include partial water changes and physically removing the foam with a skimming net.

These solutions will only temporarily solve your foam problems. All of those organics that caused the foam will remain in the pond, eventually leading more foam to form.

The Long-Term Fix for Pond Foam

To permanently fix excessive foam, you’ll need to reduce the amount of organic material in the pond. Organics come from fish waste, spawning, leaves, algae, fish food and anything else that can break down in the water. Creating a balanced ecosystem can help reduce this nutrient load, leading to overall healthier water conditions.

How Do I Reduce Organic Material in My Pond?

Reducing the amount of organic material in the pond has lots of benefits beyond reducing foam. It can also help prevent algae, reduce maintenance and keep fish healthier.

Follow the seven tips below to get started:

1. Install a Pond Skimmer

A pond skimmer is a device you install at the edge of your pond to skim floating debris off the surface of the water before it has a chance to sink to the bottom of the pond.

Skimmers significantly reduce the nutrient load in the water, leading to a healthier environment for fish, less algae and a lot less maintenance for you. We install skimmers in every pond we build, and they’re the No. 1 improvement we recommend for anyone struggling with water quality issues.

> Learn more about the benefits of pond skimmers

Skimmers are relatively easy to install if you have a rubber-lined pond. If your can’t install a full skimming system (i.e. if you have a plastic pre-formed pond), floating skimmers are also available.

2. Feed Fish Less

Uneaten fish food is one of the many organics that can break down in your pond to create foam.

Only feed your fish about once a day, and only give them as much food as they’ll eat within a few minutes of you throwing it into the pond. Reduce feedings during cooler weather, and don’t feed at all when water temperatures are consistently below 55 degrees.

Using high-quality floating pellets will also help reduce the amount of organic material in the pond.

3. Check Your Fish Load

Having too many fish in your pond can lead to all kinds of problems, including excessive foam.

So how many fish can you safely house in your pond? The answer depends on the quality of your filtration. A large pond with poor filtration can hold fewer fish than a small pond with excellent filtration. You’ll know you have too many fish if you have persistent water quality issues, high ammonia levels and/or unhealthy fish.

> Learn more about determining the best number of fish for your pond

If you find yourself with too many fish, you have three options: give some away, expand your pond or improve your filtration.

4. Improve Your Filtration

A good filtration system will include two types of filters: mechanical and biological.

Your pond skimmer provides the mechanical filtration by physically removing about 90 percent of the debris that enters the pond before it has a chance to sink to the bottom.

A biological filter, meanwhile, will provide a place for beneficial bacteria to colonize. These bacteria play a crucial role in your ecosystem by breaking down organic materials, helping to keep water clear and fish happy and healthy. Biofilters usually take the form of a BioFalls in smaller ponds, or constructed wetland filter in large ponds. Small pre-formed ponds can alternatively use a MicroFalls or Pond Filter Urn to help increase biological filtration.

5. Add Regular Doses of Beneficial Bacteria

Beneficial BacteriaBeneficial Bacteria is the cornerstone of any pond ecosystem, and it’s the primary water treatment we use to keep water crystal-clear and fish happy and healthy.

Beneficial Bacteria consume excess nitrites in the water. These nitrites, if left unchecked, can go on to feed single-cell algae.

Add Beneficial Bacteria to your pond at least once per week, or use an automatic dosing system to do the work for you. The bacteria will help create a more balanced ecosystem, while also helping to reduce the amount of foam-causing organics in the pond.

Sludge Remover is another type of beneficial bacteria that specializes in reducing built-up muck in your skimmer and the bottom of your pond. Use it in combination with regular Beneficial Bacteria as needed to keep your pond looking and performing its best.

6. Add Plants

Plants help keep your ecosystem balanced by consuming excess nitrates in the water. These nitrates will feed string algae if allowed to flourish, and as string algae decays, it can contribute to pond foam.

Add a wide variety of plants for the best defense against string algae. Each color, shape and species of plant consumes a different kind of nitrate – so the more plants you have, the less string algae you’ll have.

> Learn more about string algae 

7. Keep Up with Pond Clean-outs

No matter how meticulously you keep up with your pond, you’ll eventually end up with some amount of organic muck on the bottom of the pond.

Performing a full pond clean-out every one to three years removes this muck, preventing the build-up of organics that can contribute to pond foam.

> Learn more about pond clean-outs