What Are The Different Types of Pond Algae

By Algal Web

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Algae is something that most people look onto with disgust because those slippery green growths can make ponds look all dirty and they can be hard to remove.

But these simple single-celled algae planktonic plants are extremely important in our world. There are over 150,000 known types of algae found on our diverse planet. These organisms are responsible for producing up to 80% of our world’s oxygen and are also a valuable food source for marine and water life.

Learning to identify the different types of pond algae can help you figure out which varieties will benefit your fish life, which will be a nuisance, and which could be harmful to your pond. 

Do Ponds Need Algae?

Most people assume that algae are bad for a fish pond. While this can be true in some cases, this type of bacteria can offer you numerous benefits.

The right type and amount of algae can oxygenate the pond water, feed your pond animals, offer sheltering from the sun and carnivorous bird species, and can offer other benefits.

But too many algae or the wrong type of algae can be toxic to your animals, causes unpleasant odor, and can make your pond look slimy while suffocating other plant life.

Your pond can definitely benefit from good algae types in moderate quantities but the wrong types can also cause a lot of harm. 

The Most Common Types of Pond Algae

There are many different types of algae bacteria that can grow inside a pond. Ponds are ideal habitats for these bacterial growths because the still, warm waters optimize growth. Let’s take a quick look at some of the good types that you can boost in your pond and have a look at types that you should remove or control the moment you notice them.

Algae That is Good for Ponds

Some forms of algae are good for your pond. But too much of a good thing can be bad. Even good algae need to be controlled or it could affect your ecosystem. Here is a quick look at good species of algae that pond owners can keep and monitor in your pond.


This is the most common type of pond algae and is found in just about every type of body water. Diatoms tend to float free on the water surface but can sink to the bottom. They can thrive in any climate and any type of water from fresh to salty or dirty. Diatoms are good for your pond because they nourish zooplankton which, in return, nourish the fish in your pond. Diatoms are the best algae for ponds because it promotes a healthy ecosystem. 

Nitella or Stoneworts

This type of pond algae is often mistaken for plants. They usually grow below the water surface, are soft to the touch, and can vary in shades of green. Nitella is helpful for creating a habitat for aquatic insects that are eaten by pond fish. 

Chara or Muskgrass

This plantlike alga is also known as horsehair algae and grows under the water surface and has a musky smell with a gritty feel. It is also a good pond alga because it creates a habitat for aquatic insects that fish can eat. Muskgrass can also stabilize sediment at the pond base so other water plants can flourish. 

Carpet Algae or String Algae

This type of algae loos a lot as hair stands with their long thin designs. They tend to grow at the bottom of a pond on rocks but they can also float in large mats. Carpet algae are not toxic and act as a natural food source for many fish species like siamese algae eaters, pond loaches, and koi fish sometimes eat these growths. 

Green Pond Algae

This bacteria is also called Chlorella or Closterium algae. Green water algae are free-floating microscopic growths that can make the water look green. Green pond algae tend to grow on the water’s surface and their blooms are pretty visible. The algae do need to be controlled but it is not toxic. The microscopic organisms and zooplankton that fish eat, love to eat green pond algae. 

Algae that is Bad for Ponds

Some algae species are terrible for your pond and animal life because they produce toxins or they multiply too fast. Heavy growth can create a blanket of slime that covers your pond surface which can affect your water quality.  Here is a quick look at the worst forms of algae to have in your fish pond.

Blue-Green Algae (BGA)

Blue-Green algae is considered the worst because it isn’t really an alga at all. BGA is a cyanobacterium is an aquatic plant that produces many toxins that can affect the skin, liver, and nervous systems of people and animals that could result in death. The slime will also create a blanket that covers the entire and surface. This layer can block sunlight which will disrupt your aquatic ecosystem. 

These growths can start in small patches and will eventually take over to make your pond look like pea soup or can look like spilled green paint on the water surface.

Golden Algae

Golden algae are toxic to fish. This type of algae will give water a golden-brown appearance and grows on the water surface. Small amounts of this yellow-green algae won’t cause much harm but large quantities and the algal blooms of this bacteria can be toxic. 

Red Pond Algae

This common pond algae also aren’t really algae. This aquatic plant is a protozoan that looks red and can grow in any water body but flourishes in warmer temperatures. These protozoan growths can be toxic to fish and are known to affect water quality in ponds. 

How Do You Control Different Algae Types in a Pond? 

Bad algae types should be treated and killed or they could affect the ecosystem of your koi pond or they could poison your animal life. But good algae types should also be monitored because too much of a certain species can be harmful. 

A good way to control the algae in ponds is with healthy algae bacteria populations. Healthier algae compete with other species for excess nutrients. When the food sources of algae are limited, bad varieties can start to starve and die. 

You can also kill bad algae or control good algae by applying water treatments or by investing in high-output UVC bulbs. These UV bulbs can keep algae from floating on the surface of your water features. Water treatments will also keep healthier alae type in check. 

A proper pond filter system is one of the best methods for controlling algae growth so you can keep your alga levels balanced. 

Final Thoughts

With a proper filter system, weekly algae bacteria introduction, a UV bulb system, and the right water treatments, you can keep your different types of pond algae under control Your pond will become an ideal habitat for you and your beautiful fish species.We do hope that this guide helped you identify the good and bad pond alga varieties so you will know what treatments to offer. If you have a tough time controlling the algae in your pond then you should hop over to some of our other guides where we share the best secret and tips to help keep your pond in great condition.

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