How to Eliminate Brown Algae in Saltwater Tanks

The brown algae that appears in a saltwater tank is generally a sign of excess nitrates and/or silicates, or of poor lighting and circulation. Brown algae often appears during the "cycling" process, which is when a new tank is left running before putting in fish. Normally, the brown stuff will disappear once the tank is sufficiently cycled. In a mature tank, low-lit corners may be especially prone to brown algae. If your tank is suffering from an excess of brown algae, you will need to clean the algae out as well as eliminate the cause of the algae.

Things You'll Need

Gravel vacuum
Reverse osmosis (RO) or distilled water
Siphon
Toothbrush

Instructions

- 1
  Reduce your tank's nitrates by performing monthly 30 percent water changes. Vacuum the substrate well during water changes to remove organic waste and uneaten food. Routinely clean your filtration devices and check that they are running properly. Consistently high nitrates, even with routine water changes and sufficient filtration, may indicate that you are overfeeding your tank.
- 2
  Use reverse osmosis (RO) or distilled water when topping off your tank to counteract evaporation. Dechlorinated tap water often contains silicates.
- 3
  Change the saltwater mixture you use to make your saltwater, as some mixtures contain silicates. Some sand also contains high silicates, especially if taken directly from a beach.
- 4
  Increase lighting and circulation. Turn on your tank's lights for at least six hours a day but no more than 10 hours a day, though keep in mind that an over-lit tank will form green algae instead of brown. Brown algae often occurs in corners where light and air does not reach. If this is the case, you may need to rearrange your rocks, coral or decoration. Adding an air stone or increasing the flow of your pumps may help circulate oxygenated water.
- 5
  Siphon brown algae off rocks, glass or coral. If necessary, use a soft-bristled toothbrush to gently remove brown algae.