How to Get Rid of Pond Scum

Pond scum is a common nuisance to pond owners. It’s unsightly, smells bad, and can even kill your fish.

The good news is that there are many ways to get rid of it!

In this post, I will outline the best methods for getting rid of pond scum and give some tips on how to prevent it from coming back.

What is Pond Scum?

Pond Scum
Typical Pond Scum | Photo by Livescience

Pond scum is a thin layer of bacteria, algae, and other microorganisms that grow on the surface of ponds.

There are many different types of pond scum. Some can be harmless or even helpful to your pond while others can cause health problems for fish and humans.

The most common type is cyanobacteria which release toxins into the water when it dies off in large numbers from overgrowth or low oxygen levels. It’s important to know what type you have so that you can take precautions against possible dangers!

Identifying Pond Scum

If you are worried about what is the brown or green scum on your pond, you can figure it out by hand test.

Pick up the scum in bare hands and feel the texture. If you find it slimy, it is probably algae.

What kind of algae it is?

You can use a weed identification tool to know that.

If the algae mats together like wet hair, you can call it filamentous algae. Filamentous algae are one of the most common kinds of pond scum.

There are other kinds of pond scum. If the plant looks like the sole of a man’s shoe, it is duckweed. It is also called a duck meal. The shape of the plant is like a small eraser. It comes in different shades of green color. These weeds are also algae.

These aquatic weeds or scums are not toxic to touch. But it is wise to wash your hand with soap after the hand test.

Different Types of Pond Scum

Identifying different types of pond scum is a challenging task. Pond scum can be identified by hand tests which I described before. Here are the characteristics of the most common type of pond scum.

  • Filamentous: As its texture is like a wet hair mat. It stubbornly attaches itself to the bottom of the pond. Too much filamentous deplete the oxygen supply into the pond water. It causes the death of the pond fish.
  • Chara: It has grown on the bottom of the pond. Its texture is musky and rough. It grows on a pillow formation.
  • Oscillatoria: It comes with blue, blackish green color. It makes the watercolor red or purple
  • Microscopic: You cannot identify this pond scum with bare eyes as it is too small. It changes the watercolor to brown or soup green.

Is Pond Scum Dangerous?

Pond scum is the biggest problem for pond keepers. An excess amount of pond scum reduces the good bacteria and nutrient value of pond water.

Pond scum creates a dense layer on the surface of the pond and doesn’t let the sunshine enter into the water. Good bacteria cannot work properly without sunshine.

Lack of sunrise also reduces the nutrient value and quality of the water. Pond scum odors hydrogen gas. It affects the ecosystem which is harmful to the fishes.

What Causes Pond Scum?

So, what causes pond scum?

It is a natural phenomenon. When the level of specific nutrients increases in the water, pond scum grows.

Pond scum grows phenomenally. Warm water is the ideal environment for algae growth. On the other hand lack of maintenance also causes pond scum.

How to Get Rid of Pond Scum

Natural Remedies

A natural solution is always the best solution. All the pond scum or algae are not harmful. One big disadvantage of using algaecide, it kills all the algae. It is not good for the ecosystem of the pond.

Chemical algaecide may also harm the fish. It consumes the nutrient value of the pond water. So, natural remedies should be chosen first.

Pond Skimmer or Net

It is the simplest way to clean pond scum. You can use a Pond Skimmer or net to remove pond scum.

You can also clean the leftover fish food and floating debris with a pond skimmer. It will implicitly help you to reduce pond scum.

Using Pond Snail or Fishes

Some snails are used to reduce the pond algae. As pond scum is one kind of pond algae. You can use snails or tadpoles. It eats up a large amount of pond scum.

There are also some algae-eating fishes such as twig catfish, cherry shrimp. Amano shrimp, Siamese Algae eater, etc.

Aquatic Plants

Aquatic plants are also a great solution to reduce pond scum or algae. It absorbs the excess nutrients which cause starvation of pond scum.

Some floating plants such as lilies and lotus work as the shade on the water. It reins the excess sunlight.

Some aquatic plants also consume excess nutrients. You can use those plants to solve the pond scum problem.

Rock Salt

Using rock salt is another solution for reducing pond scum. Mix a pound of rock salt with 100 gallons of water. Don’t use it excessively. It may cause harm to fishes and plants.

Barley Straw

As all the pond scum are not harmful, you can use another process of controlling the pond scum growth without killing it. This is barely a straw mechanism. It prevents the additional growth of the algae.

Keep the barley straw in the water. When it starts to decompose, it releases one kind of chemical which prevents the growth of algae.

Barley straw works great in sunlight, as it requires more oxygen to decompose.


Precaution is always better than cure. As leftover fish food causes pond scum. You can try to not overfeeding your fishes. It will help you to get rid of the pond scum.

Excess sunlight causes the growth of pond scum. It makes the pond water warmer. You can use shade on the pond water to prevent this problem. It is one of the permanent solutions for treating pond scum.

Clear pond water free from scum
Pond free of scum | Photo by CLear-water-revival

Chemical Remedies

It is not the primary solution. When it becomes very difficult to control the growth of pond scum, you can use algaecide or medicine.

I recommend you to start AM Leonard’s 4 step pond scum cleaning program. It will help you to clean your pond entirely.

Crystal Blue Lake & Pond Treatment

It helps to maintain the color of the pond water. It should be applied from February to November.

This medicine shouldn’t be used on a rainy day. It will lower the volume of the color. It cleans up the scum and brings back the color of the water.

It also helps to dissolve solid materials. 1 Gallon of medicine is enough for 1-acre pond water.

Natural Pond Cleaner

It recovers the muck of the pond. It also cleans dead algae, fish, and debris. This algaecide helps to increase the number of healthy bacteria.

Healthy bacteria reduce excess nutrients in the pond which causes a reduction of pond scum. Apply it from February to November for the best result.

Crystal Plex Aquatic Algaecide & Herbicide

It kills the pond scum directly and keeps the water clean. This medicine should be used when the previous two steps are not enough for reducing the growth of the pond scum.

It should be applied from April to September. It Controls Filamentous, Chara, microscopic, etc. It is a long-term solution for treating pond scum.

This chemical is not harmful to humans, pets, and birds. But it should not be used in the koi pond. For one acre pond, mix at least 10 gallons of water with 1-gallon medicine. You can spray it directly on Filamentous

Tsunami DQ Aquatic Herbicide

It is excellent for controlling duckweed, coontail, slender leaf weed, etc. Its active ingredient Diquat and is used to kill the tougher pond scum mats. It immediately works. It burns down the stubborn floating weeds

Keep it away from the children.


I have discussed the primary steps about how to get rid of pond scum as well as the additional steps. Hopefully, this guide will help you to reduce the problem.

Besides these steps, regular pond maintenance is very important to keep the pond clean and healthy. So, take care of your pond and follow the above guide to get the best result.

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