Algae in the Fish Tank: Benefits, Cures and Prevention

Are algae bad for fish? Are algae good for my aquarium? How do I get rid of algae in the fish tank? We get so many questions like these, and don’t worry; we’ll cover all these questions and more in this article so that you have everything you need to know about how a little bit of green can keep your water clean and beautiful. 

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To answer it simply, algae are not harmful to your fish; still, there is a negative connotation to their existence in the fishkeeping community. Contrary to popular perception, algae are a natural part of the ecosystem in some bodies of water. It serves as food and habitat for many species, which would otherwise not exist without them. However, in some instances, they can be quite a danger for fish.

What are Algae, and what is their role in the ecosystem?

Algae is a kind of bacteria found in many places like the ocean, lakes, ponds, and sometimes even in your small fish tank. It’s a diverse group that includes microscopic phytoplankton as well as macroscopic forms such as seaweed.

Common Types of Algae

Green Algae:

The most common algae on Earth are chlorophytes or green algae with large cells containing photosynthetic pigments called chloroplasts.  They can be found as plankton in both salt and freshwater.

Red Algae:

The second most common type of algae is Rhodophyta, also known as rhodopsin algae, which contains phycoerythrin. They can be found in both salt and fresh water, but unlike green algae, they don’t need light to survive, so they only grow at depths under 20 feet where other forms of life cannot go. The red color is due to a carotenoid named fucoxanthin that absorbs blue-green wavelengths from sunlight very easily while reflecting yellow/orange colors. This creates an effect similar to camouflage for them when exposed to rocks or sand bottoms.

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Brown Algae:

Brown algae are diverse species that live on the seabed, rocks, and sandy seafloor at all depths, from shallow water to deep ocean trenches. They have more complex cell structures than their green counterparts because they contain chloroplast and carotenoid pigments to store energy from sunlight. This gives them their brown coloration and other distinguishing features. Brown algae are important food sources for many sea creatures and play a significant role in the ecological system by recycling organic matter, binding heavy metals found in wastewater to prevent them from being washed into streams or lakes, and protecting coastal areas from erosion.

Pros and Cons of having algae in your fish tank


  • Some people like watching plants grow, which helps them relax while they watch their fish swim around, so algae could also make an excellent addition if you were trying to create a serene environment for certain housing types of fish like betta.
  • Another benefit is that there will generally be less dirt built up on stones and leaves because microorganisms break down organic matter so they can eat it.


  • One drawback of algae could be there existence if you do not want any type of bacteria developing near your tank’s waterline. 
  • Algae thrive off decaying material from higher levels, including mulm from the bottom, and may release toxins harmful to your fish. 
  • To remedy this,  you would need to periodically clean the rocks and leaves of any algae so that it does not get too out of hand. 
  • If you notice that the algae in your tank start to produce a smell or get too thick, this may indicate an imbalance with nutrients or other water parameters.
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How to maintain algae in the fish tank without risking its healthy environment?

  • You should keep an eye on your tank’s algae levels by periodically checking the surface of the water and keeping tabs on any changes in its color or texture.
  • If you notice a significant growth pattern, this may be due to excess nutrients from fish food leftovers, overfeeding, or decaying plant matter rotting at the bottom of the tank.
  • Ensure there are no excess nutrients and that the surface area for light isn’t blocked out with large plants or dark-leaved ones like Java Ferns.
  • A major change in sunlight could also trigger algae blooms because they need natural amounts of UVB rays to grow properly without interference from other organisms.
  • If you notice more of an algae problem, try changing around your decorations, so they’re not blocking out natural sunlight as much when it passes through them.
  • You can also cut down on feeding if you find overfeeding has been causing major blooms from leftovers at the bottom of the tank.
  • Another idea would be to purchase live plants which do not block out any natural light sources below their leaves, such as Anacharis. However, this plant will still need ample amounts of light to grow properly.


Algae is an inorganic type of plant life that grows under certain conditions, and it may be harmful to the fish if it excessively grows on rocks and plants because some types release toxins into the water. Some varieties are beneficial as well because they provide food for tiny organisms. I hope you’ve found the answers to any question you had in your mind about algae through this article. Support this blog by subscribing to our RSS feed.

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