Reef tanks require good lighting for proper growth of invertebrates that have algal cells growing in their tissues. Strong lighting also spurs hair algae growth. (Fact of life, plants grow faster with stronger light--chlorophyll etc.) The main problem is evaporation, though. 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 PHOSPHATES = 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! Of course algae growth fertilizers generally have phosphates also. Some sea salt mixtures have more phosphates than others, so read up on these and use one with the lowest phosphates possible.
The following is a list of things to be done:
1.Install an R/O unit and use only R/O water for water changes and topping off for evaporation.
2.Use a good quality protein skimmer. (The biggest you can find.)
3.Use only trace elements, foods, fertilizers, carbons, etc. that contain no phosphates or silicates!
4.Use Phosphate Sponge (this product is not a sponge but actually a regenerable granular ceramic product) to remove phosphates and silicates now present. Continued use will insure any phosphates accidentally added will be adsorbed and removed from the system.
5.Make sure your protein skimmer is large enough. There has been debate about overskimming a tank and whether one should skim a tank at all. But when a tank is new or when there are algae problems, "size" always helps.
6.Remove all the hair algae you can.
7.Stop adding any trace elements or supplements. Algae are very opportunistic and additional trace elements or supplements will often boost growth. The major element to control is iron. If a product doesn't list its ingredients (some proprietary supplements don't list the ingredients), don't add it to the tank since you might be adding something that will greatly increase algae growth.
8.Vacuum detritus regularly and practice good tank maintenance.
9.If you are already practicing the above, your other problem may be old lamps (more than 6 months). Lamps continue to burn, but since their spectrum has shifted, they will assist hair algae, and not help corals and photosynthetic inverts like they should. Change bulbs every six months! The other problem with lighting is too long a photo period. Many aquarists run metal halides or
VHO fluorescents for 10 to 12 hours a day. Hair algae is very opportunistic, you will never get it under control with this much light. Reefs don’t get 12 hours of "high noon" sunlight anyway. We recommend that you get some 40 watt fluorescents to run 10 hours per day and run your metal halides or VHO’s only 4 hours per day. While getting the hair algae under control limit them to 1 to 2 hours!
10.Critters that eat Hair Algae are: Scarlet Leg Hermit Crabs, Blue Leg Hermit Crabs, Hypselodoris bullocki and Astrea Snails. Purchase about one astrea snail per gallon of tank capacity. (This sounds like too many snails but is the amount required to do a really good job.)
11.Introduce additional detritivores. If excess food isn't eaten, it will decay and add to the nutrients and waste in the tank. Addition of bristle stars, bristleworms, hermit crabs, Nassarius snails and sea cucumbers will help control the excess food that a reeftank's primary fish and invertebrates don't consume.
Okay now tell me what you have done and what you havent based on this list. We can go from there.