When I had hair algae I did a number of things. I began running carbon in addition to phosban, I then made one of the smartest live goods purchase I have ever made, sorry make that 2 purchases. I bought a lawn mower blenny who's main diet is algae, and then for 5 bucks I bought a pink pin cushion urchin. I put the urchin in my 20 gallon QT tank and then I would put any rock with hair algae on it in that tank. The urchin would clean the rocks within a day or two, he is very good at his job. Now you could put this type of urchin in your main display but they are bad about picking up corals that are not glued down and taking them on thier back all around the tank,, which is why he is in my 20 gallon QT. So you could keep him in the sump.