Hair algae are a common problem in both freshwater and saltwater fish tanks. These clusters of hair-like organisms come in a variety of colors, including green, red, blue, brown and black. The color variations between hair algae phyla evolved to allow the organisms to absorb different wavelengths of light at different depths and light exposures. Hair algae are a fast-growing algae. Because saltwater aquariums require a more delicate mixture of elements than freshwater ones, they are more susceptible to severe ecosystem disruption by hair algae infestation.
White Hair Algae
All phyla of hair algae lighten towards white in the reproductive stage, when spores are produced and disseminated. If hair algae is white the first time you notice it, it means the algae has been present but was camouflaged by its color until it went into spore-production mode. The appearance of white hair algae in saltwater aquariums must be taken seriously and treated as soon as possible.
A thorough cleaning of the tank should be your first step upon discovering white hair algae in a saltwater aquarium. This means cleaning everything; pumps, stones, rocks, coral, shells and sand. A simple rubbing will remove the algae, but care must be taken to wipe every surface. For this reason, toothbrushes or similar must be used to clean anything in the tank with an irregular surface. Obviously, this makes a reef tank one of the toughest to rid of hair algae.
Once cleaning is done, preventative measures must be taken, as hair algae appear for a reason and until the reason is removed, the problem will reoccur. Algae need three elements to thrive; water, light and nutrition -- in the form of nitrates and phosphates. You can’t change the amount of light and water in your tank without endangering your fish and plants, so that leaves nitrate and phosphate control.
Phosphates and Nitrates
Uneaten fish food and fish waste products are the principle, and sometimes only, source of nutrition (phosphates and nitrates) in your tank. The presence of hair algae indicates an excess of nutrients. The solution is to stop over-feeding. Don’t worry about starving your fish – if you have hair algae, your fish are well fed and will do fine for a few days without feeding. After cleaning the tank to remove hair algae, don’t feed your fish for 72 hours. When you do feed, stay at the tank throughout the top-feeding process. Add a bit, wait for it to be eaten and then add a bit more. Do not feed your tank more than the top-feeders consume in 30 seconds. Use this method to determine the proper amount of food.
Tap water can contain phosphates. Consider using RO/DI, reverse osmosis/de-ionized, water if hair algae reoccur despite cleaning and proper feeding. Animals that feed on hair algae include turban and Nerite snails, as well as emerald crabs.