Q: I have a hair algae problem. What can I do to keep it under control?
A: Green hair algae is probably the most annoying problem that most reef aquarists face. The problem rarely occurs in fish only tanks because the algae is inhibited by copper treatments for parasites. Reef tanks, however, almost always suffer from bad growth of hair algae due to the fact that they can not be medicated, because the same copper that kills ich and oodinium will kill all invertebrates.
What is a reef aquarist to do? First, lets see why the problem occurs. Reef tanks require good lighting for proper growth of invertebrates that have algae cells growing in their tissues. Strong lighting also spurs hair algae growth. (Fact of life, plants grow faster with stronger lightchlorophyll etc) The main problem is evaporation, through. High evaporation rates, combined with city water, high in PHOSPHATES, spell sure trouble with hair algae. Although lighting and other things contribute, the point to remember is PHOSPHATE = HAIR ALGAE. Stop the phosphates and the hair algae growth will stop, or at least come down to a manageable level where snails etc. can keep your tank looking good.
Phosphates generally enter through city water, but some "trace element" mixtures available on the market have substantial amounts of phosphates. In fact, the two best known trace element supplements, have phosphates added on purpose, so BEWARE! (Kent Marine Essential Elements is an excellent trace element supplement without phosphates or silicates!) Of course algae growth fertilizers generally have phosphates also. (Kent Marine Micro Algae Iron Supplement with Manganese has NO PHOSPHATES OR NITRATES1) Some sea salt mixtures have more phosphates than others, so read up on these and use one with the lowest phosphates possible.(Recommended salts are Instant Ocean, Reef Crystals and of course Kent Sea Salt) Several popular calcium and strontium supplements contain gluconates or other sugars. One new product promises to "turbo charge" natural enzyme systems and can cause ich to go dormant. That product is loaded with sugars. There is some evidence that hair algae can make use of these carbon sources, so beware! They also will cause other problems such as cyanobacteria growth. Sugar has no place in a reef!.