7 Common Types of Algae Found in Freshwater Aquariums

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If you see something green and fuzzy growing on your tank surfaces, it is probably some kind of algae. Not all algae is green, however, and it might not all be fuzzy. There are a number of different types of algae which can be found growing in freshwater aquariums. Know your algae – here are seven different types of freshwater algae you might encounter and how to control them.

Related: Tips for Keeping Your Aquarium Water Quality High

Most Common Freshwater Algae Types

There are many different types of algae which grow in aquatic conditions but there are seven that are most commonly seen in freshwater aquariums. These seven types of algae are:

  • Brown Algae: This type of algae is most commonly seen in tanks with high phosphate or nitrate levels. Brown algae is also common in new tanks but it generally goes away after the tank has cycled properly.
  • Green Hair Algae: This type of algae grows in long, wispy threads and it is sometimes called thread algae. This algae is usually green in color, though it may also be brown. Hair algae is easy to remove but it quickly returns if the conditions responsible for its growth are not remedied.
  • Red Algae: This algae can be found in both freshwater and saltwater conditions and it is multicellular which gives it a rigid structure. Red algae is also sometimes called beard algae or brush algae but these are all different types of red algae.

Related: Setting a Schedule for Routine Tank Maintenance

  • Green Algae: This type of algae is most commonly seen in aquariums with very bright lighting and it can grow on tank objects as well as in the tank water. Sometimes green algae will cause an algae bloom which turns all of the water in the tank green.
  • Blue-Green Algae: Technically, blue-green algae is actually a type of bacteria called cyanobacteria and it is most commonly found in very nutrient-rich waters. Most freshwater fish do not eat blue-green algae but some freshwater snails like Nerite snails do.
  • Black Algae: This type of algae is commonly found in planted tanks and it grows in dark black spots that may be fuzzy in texture. Black algae is often seen in the roots of slow-growing plants and in filters.
  • Diatoms: This type of algae is brown in color and it may show up in spots on the walls of your tank or on other tank objects. Diatoms can be found in both freshwater and saltwater environments.

Tips for Controlling Freshwater Algae

The secret to controlling algae in your freshwater tank is to limit the things algae needs to grow. You cannot reduce your water level without affecting your fish, but you can take away other key nutrients like light. Algae is most likely to grow in tanks that are placed in direct sunlight and in tanks that have a surplus of artificial lighting. Keep your tank away from windows and only keep your tank lights on for 10 to 12 hours per day. You can also limit the nutrients that algae needs to grow – this includes nitrate and phosphate. Using an aquarium filter and performing water changes to keep the water quality in your tank high will help you to accomplish this goal. Another option is to stock your tank with algae-eating fish or invertebrates. Most species only eat green algae, but you can find species that specialize in eating certain types of algae if you do your research.

You may not be able to completely prevent algae from growing in your freshwater aquarium, but there are plenty of things you can do to limit its growth. By controlling lighting and nutrients you can reduce algae growth and adding algae-eating species of fish will take care of any leftovers.