In my current tank I haven't seen any hair algae. There may have been a little on one of the pieces of live rock that I put in the tank. However, it quickly disappeared. This tank is definitely dominated by the pinks, purples and even some greens of Coralline algae. It continues to spread like crazy. When I saw the the first circles of the algae on the glass I was overjoyed. Now, however, the algae is starting to become somewhat of a pain. I have a hard time keeping up with it. Even though I clean your typical green, red and brown algaes off the front glass every few days with my magnet cleaner this doesn't keep the coralline under control. Once it takes root it has to be scraped off with a razor blade. It is especially bad at the sand bed where I'm afraid to clean with the magnet cleaner for fear of trapping sand in the cleaner and scratching the glass.
The following pictures were taken yesterday. This is approximately five months after starting my tank.
If you are curious you can look at the pictures from January 13th, 2008 and October 17th, 2007 for reference.
I know lots of people would love to have this problem. It does indeed look nice and I don't want it to go away. However, it does tend to increase the maintenance that has to be done. So what am I doing to get the algae to grow so rapidly? I'm not completely sure but here is a list of things that I bet contribute:
1. Only RO/DI water goes into the tank. Never a drop of tap water.
2. 48" Odyssea 260 Watt Power Compact Lights from the Fishman on eBay w/ stock 10000K daylight bulbs and true actinics. Daylight bulbs go on at 8:00 am and turn off at 10:30 pm. Actinics turn on at 7:45 and turn off at 10:45. So, I have roughly 14 1/2 hours of lighting in the tank.
3. Dose with 15 ml of each part of Oceans Blend two part calcium and pH/Alkalinity daily. Well almost daily. If I sleep in after 8:00 on the weekend (pretty much every weekend) I won't dose since the instructions say to dose before the lights come on to avoid pH spikes. My calcium level is at 460ppm.
4. Dose with 1 1/2 cap fulls of Kent Marine Tech I iodine each Sunday.
5. Water change using Instant Ocean every 3 to 4 weeks.
6. Use a protein skimmer.
7. Last but not least live rock. Unlike other algae in your tank the coralline won't show up unless you seed it. You need to add live rock. The rock I bought had a lot of coralline growing on it already. The quality of your rock probably makes a big difference.
That's all I can think of. Good luck on getting Coralline to grow in your tanks.