How to Get Rid of Black Brush Algae

Updated July 18, 2017

Black brush algae is a type of red algae from the family Audouinella. It can be seen growing as short black tuffs or a slow spreading carpet in aquariums. Generally, algae need light, carbon dioxide and nutrients to grow. An aquarium that has high nutrient levels or is not filtering out the fish waste and food properly, provides a great environment for algae to grow. Although black brush algae can be challenging to get rid of, it is possible. Removal techniques include changing the aquarium conditions, introducing algae eaters, refreshing the water, limiting leftover food, scraping and chemical additives.

Measure the dissolved CO2 content in the aquarium water. Do this every day for a few days to make sure that the level stays between 25 and 30 ppm. If the level is fluctuating, introduce fast growing plants and add a liquid CO2 product. Commercial testing kits can be bought from aquatics stores.

Measure the nitrate and phosphate levels to make sure they are in the proper range. The nitrate level should be about 15 ppm and the phosphate level should be about 0.5 ppm. Commercial testing kits can often be found in aquatics stores.

Place Siamese Algae Eaters into the aquarium water as soon as the algae is first noticed. Limit their access to fish food so that they eat more algae. Although you can find many different types of algae eaters, those from the species Crossocheilus siamensis are known to eat black brush algae.

Scoop up to 10 per cent of the aquarium water and replace it with fresh water. Do this weekly to keep the nitrogen and phosphate levels low. These algae nutrients often come from fish waste and food that is left to dissolve in the water. Don't do this if a fluctuating CO2 level is the main cause for black brush algae. The addition of fresh water will alter CO2 levels.

Sprinkle small portions of fish food into the aquarium at meal times. Wait for the fish to finish before giving them more. This will help lower the amount of food being left to decompose into nutrients for the algae.

Pull all infected plants and material from the aquarium and throw them away. Scrape the black brush algae from the tank walls or equipment using a razor blade. Make sure that any items put back into the tank are free of algae.

Squirt a dose of commercial aquarium carbon into the water. Do this every day to kill off the black brush algae. Scoop any loose or floating algae out of the tank.

Things You'll Need

  • CO2 test kit
  • Nitrate test kit
  • Phosoohate test kit
  • Siamese Algae Eaters
  • Bucket
  • Razor blade
  • Carbon
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About the Author

Patience Lister has been conducting research on natural health products and functional food since 2005. She has been writing since 2009 and has contributed to "Canadian Running Magazine," "iRun Magazine" and "The Vancouver Sun." Lister has a Bachelor of Science in biology from the University of Victoria and a diploma in food technology from the British Columbia Institute of Technology.