[Chin_Lee]

I used Phosgard at 1/2 recommended level but left it in the sump and it went away by itself. I have a 180 FO with refugium of algae and mangroves, light fish load (3 medium size fish and 13 small fishes) for a setup. At one point, I could not see any of my rocks except where coralline were growing. I put Phosgard in and within a week the hair algae were getting thinner. MAKE SURE YOUR SKIMMER is working at PRIME PERFORMANCE level or else it doesn't matter what you do, it will grow back as more die. Then I used a Mag 5 that I am using for internal circulation against the hair algae and they will dislodge from the rocks and make your tank look like crap. But keep the prefilter on the Mag 5 and clean it and/or your tank intake every hour until it clears.
HIH
CWLee