HimandHer, Here's my speach I've posted a couple(few) of times on the actual only thing I will claim to be an expert on when it comes to reefs. I'm gonna give you my advise on the nasty hair algae curse. Not everone will agree with me on all of what I have to say but I can asure you I've had a reef up for over eight years + and I've been to hell and back with this stuff and I'll tell you what works, for sure, some of the time, part of the time, and non of the damn time. It is true that hair algae loves phosphates and silica, and ofcourse light, and eliminating or reducing these things will help curb it to a degree, but here's the thing a perfectly healthy reef with good water quality can grow hair algae, especially if your reef has ever had it before! Water changes are the quickest way to get your PO4 under control assuming your using RO water or a water source that has no PO4 in it. Here's the hard part and the part that always pisses me of when people pipe off and say it, that is, all you have to do is worry about water quality and get it right and the hair algae goes away. Not true! The hair algae that is in your tank stores enough nutrients within itself to grow at an alarming rate with perfect water readings! Dont be fooled just because the cheap Charlie test kits we all have read zero. Testing phosphates is fine, I do, but does it really matter? No matter what the test says you gotta problem. Its like a heart problem, once you have one, you dont cure it, you manage it! So, here's my 2 cents on how to get rid of it including all the blatently obvious overplayed things that are repeated over and over again. Bigger and longer established tanks are harder to treat than smaller ones for sure. It makes me laugh when I here someone whine about an algae problem with a fifty gallon tank, gimme a break, pour it out in the neighbors yard and start over.
1) Do water changes ofcourse, but rig yourself up a rigid length of clear tubing to your siphon hose to control and vacuum up all the loose algae and reef debris. Reef dust that collects in old dead corals like trumpets and torches and such seem to be the worst.
2) To really get a head start take some of the rocks out of the tank and dip them into a bucket of salt water and scrub the ever holy liven crap out of them with a toothbrush.
3) Cutting your light time, and reducing your feedings are certainly helpful at least until you get it under control.
4) Get or make sure your skimmer is running properly! And replace your prefilter media constantly.
5) When selecting a clean-up crew, be careful not to over do it at first! Its great to have a snail for every gallon like some people say, and all the other cute little criters, and I dont totally disagree, but if you put a lot them in your tank and some die off, (and they always do) you've now created more fuel for your algae. Big time!
6) Dump in some long spiny urchins, you cant kill hardly em, and they really mow! They can tip things over though, so watch em! Their a little slow, but over all these are my favorite, and did I mention their tougher than heck!
7) The phos-ban products do help, but their expensive and with all the other factors they alone wont eliminate your algae only help manage it after you've gottin rid of a lot of it. I like the slower acting stuff for a long term preventative measure. And taking the cost of the stuff into consideration, water changes are cheaper for sure.
8) UV stearlization is good for some things, but worthless for hair algae.
9) Adding fish that eat algae is more preventative than a cure, and if you have a real problem it will only help minimally. Anytime you can just add a fish or two and eliminate your algae, you dont have a real problem. Trust me!
10) Increasing reef circulation will help by keeping the reef dust kicked up so it easier for the filters to get it out of your tank. It is kinda wierd though the rivers by my home run real fast, and they grow aglae like crazy.
11) Do the fuge thing if you can, or add some of the phosphate consuming macro's to your tank
The bottom line on all this is to get it under control you have to get a little drastic, or you wont get it under control. From that point on its prevention. Hope this helps.