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4 Unexpected Causes of Foam in Your Backyard Koi Pond

4 Unexpected Causes of Foam in Your Backyard Koi Pond

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After a long day, you head out to your garden to relax next to your koi pond. As you approach, you notice a few bubbles and fizzing on the surface.

At that point, you may wonder, why is my koi pond foaming? If that’s the case, then you’ve come to the right place.

Let’s take a look at some of the reasons your koi pond may be bubbling. We’ll also discuss how you can get rid of the foam.

Where Does Pond Foam Come From?

Since water makes up any pond, it stands to reason that when something goes wrong, it’s an issue with the liquid.

To help you understand this a little better, let’s discuss a few basic physical properties.

First off, when water is in liquid form, its particles share some connections. These intermolecular forces keep the liquid from evaporating into gas.

The forces come in two different forms: cohesion and adhesion.

Cohesion deals with how water particles like to stick together. The molecules link to each other due to the polarity of the atoms.

Adhesion, on the other hand, focuses on water molecules’ attraction to other objects.

Together, these two forces create surface tension. This produces a layer on top of the water that acts as a barrier.

It stops any particles from entering or exiting the pond without exerting energy.

When an object has enough power to break through the barrier, the tension will collapse. This will cause a foamy layer to appear on the surface.

Is Pond Foam Dangerous?

Noticing foam on the surface of a pond can be a little alarming. However, for the most part, the substance isn’t dangerous.

While it may affect the overall look of your pond, it shouldn’t harm your koi. In fact, a small amount of foam is perfectly normal and healthy for a still body of water.

Although, excessive foaming can spell out trouble. When that happens, it means that something is wrong with the water itself.

So, you’ll have to address the underlying issue before the foam disappears.

What Causes Pond Foam?

Now that you understand the basic process of foaming, we can take a look at what causes it. There are a few different reasons your pond may be bubbling up.

1 – Water Quality

One of the major factors that can cause foaming is water quality issues. This is usually a result of the organisms living in the habitat.

When we think of koi, we imagine beautiful graceful creatures swimming around. While that may be true, these fish can also be incredibly messy.

They tend to eat a lot, and in turn, produce a lot of waste. That’s why a koi pond can go cloudy after just a couple of days.

Even though you can only see the koi fish, there are hundreds of other species living in the water. Each one will hunt for food, digest it, and produce waste.

Over time, the water accumulates unwanted substances. This will change the composition of the liquid and change its properties.

2 – Feeding Quantity

An essential part of taking care of your koi is nourishing them. On average, a pond full of fish will need a couple of handfuls of food a week.

You sprinkle a small amount of feed on the surface, and you watch the swimmers crowd to grab it.

Unfortunately, that makes it a little difficult to see if each fish got its fair share of food. So, chances are you add a little more food for good measure.

While this ensures all the koi are getting enough nutrients, it can affect the water.

After a while, the food can start to break down and rot in the liquid. This may cause bacteria to grow and create foam.

3 – Spawning Habits

Another common cause of pond foam is spawning. This is when koi fish congregate to reproduce.

During this process, the fish will splash around and flail constantly. This creates strong currents in the water that’ll break the surface tension.

On top of that, the fish will crash against the pond bed and dig up some of the sand. When that happens, the water will become murky.

Finally, as the koi lay their eggs, they thrash again and release wastes. Both those actions will affect the water quality and lead to foam.

4 – Microorganisms

As part of the pond ecosystem, some microorganisms will grow in the water. For example, water mites and algae enjoy this damp environment.

While these are mostly harmless, they can affect the composition of the water. Aside from the fact that they produce waste, they’re also constantly in motion.

This movement leads to air and other particles entering the water.

How to Get Rid of Pond Foam

After you notice the foam, your main goal is to get rid of it. Well, there are a few ways you can go about doing that.

1 – Skim the Surface

One of the fastest ways to remove foam is to simply scoop it out. Using a skimmer, go over the surface and get rid of any visible bubbles.

Depending on the size of your pond, this can take quite a while. In addition, this won’t resolve any underlying issues, it just addresses the symptoms.

2 – Treat the Water

If the issue is a result of water quality, you may have to utilize other treatments. Before you do that, it’s a good idea to test your pond.

There are kits you can use to help you figure out where the flaws stem from.

Once you identify the problem, you can fix it. Most of the time, it’ll be an issue with the water’s pH. This is due to all the waste products in the liquid.

In that case, you have one of two options. First off, you can use chemicals to neutralize the water and bring it back to a healthy point.

Other than that, you can add a janitor fish to the water. That’s a species that specializes in sweeping the pond for any waste materials.

3 – Use Better Quality Food

As we mentioned, overfeeding the koi can lead to foam. Sadly, this is a little tricky to resolve.

It’s not a good idea to cut down the food portions you supply to the fish. This may lead to increased competition, and the koi can begin to fight.

Instead, a much better solution would be to find a different food source.

Before you buy fish feed, make sure you read the informational sticker. It should tell you the concentration of all the minerals in the food.

The main culprits behind foam tend to be proteins and nitrates. They affect the forces between the water particles and cause them to break.

4 – Add Filtration

If you’re not interested in the long process of testing and treating the water, you can add a filter.

Typically, ponds will rely on the plants under the surface to clean the water. The flora can absorb some of the waste products and neutralize the liquid.

However, with an overcrowded pond, the plants may not be able to do their job on their own. In that case, you’ll need an additional filter.

This will ensure that the water is clean and that there’s always a fresh supply of oxygen.

Final Thoughts

At the first sign of bubbles on the surface, you may ask, why is my koi pond foaming? There are a few possible causes behind the issue.

These include water quality, feeding quantity, and spawning cycles. In addition, some microorganisms can play a role in foaming up the pond.

When you figure out the culprit, there are a few ways you can go about resolving the problem. You can try skimming the surface and removing the visible foam.

Other than that, use water treatments or filters to keep the pond clean.

Finally, before you pick up a bag of koi food, make sure it doesn’t contain excess nitrates or proteins.


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