How to Get Rid of Black Moss From a Fish Tank

One of the problems that aquarium owners may encounter is a black moss that grows on glass, gravel and decorations. This fuzzy, blackish material is actually an algae called black brush algae or black beard algae, and it can be a stubborn problem that recurs after cleaning. Black algae is caused by cyanobacteria that looks like short hairs that grow close together similar to moss. A number of measures will help to control this unsightly problem in your fish tank.

Things You'll Need

  • Soft brush
  • Chlorine bleach
  • Utility razor blade
  • Water conditioning chemicals
  • Fish tank net
  • Algae eating fish
  • Live plants
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Instructions

    • 1

      Remove decorations from the tank and scrub with a soft brush to remove the black algae. For stubborn growth, soak the item in chlorine bleach for a few minutes. Rinse the decoration carefully before returning it to the tank.

    • 2

      Scrape the black algae from the tank glass with a utility razor blade. Remove the loose algae from the water with a fish net.

    • 3

      Turn off the lights in the fish tank for several hours each day. Algae requires light for photosynthesis and growth, so reducing the amount of light can limit the amount of algae.

    • 4

      Remove 20 percent of the tank water and replace with clean tap water. You may need to pre-treat the tap water to remove chlorine, ammonia and heavy metals before putting it into the tank. Your aquarium store has a variety of chemicals for this purpose.

    • 5

      Introduce algae-eating fish into the tank, such as black mollies or Siamese algae eaters. Not all algae-eating fish will eat black brush algae, however, so you may need to experiment to find the right fish to tackle your problem.

    • 6

      Increase the number of live plants in the tank to compete with the algae for nutrients.

    • 7

      Consider increasing the amount of carbon dioxide. Although tanks with black brush algae problems typically have high levels of CO2, according to the AquariumsLife website, aquarist Neil Frank says an injection of CO2 may help to increase the rate of plant growth; and with a large density of plants and bright light, the plants will suck up dissolved nutrients and cause algae to subside. Experiment with gradual increases in CO2 to find the right amount of pressurized carbon dioxide that allows your live plants to thrive but discourages the growth of black algae.