Is it hair algae or bryopsis? They are 2 different things. Either way, it sound like you're on the right track. When I first set up my tank, I bought my salt water from a
LFS that used
RO/DI, but I used tap for my topoff. When I swithed from 20K bulbs to 10K, the algae just exploded. It is receding now, slowly, due to several actions on my part. I was growing cheato in my hang on
fuge, but it wasn't very much. I rearanged my
sump and moved some down there with lighting and have been letting it grow without pruning. I have stepped up my water changes from 10 gallons a week to 20. I have added 2 phosban reactors. one with carbon, and one with phosban. Also, I have been removing it manualy as best I can. i just pull out whatever i can reach and put it in a bowl of fresh water, so i can dip my fingers in it and get all the little pieces off. This allows my cheato to absorbe more of the free nutrients and out compete my hair algae. After a good round of manual removal, i also blast my rocks with a powerhead to blow off all the
detritus that was trapped by the algae.
If it's Bryopsis, similar methods should work, and you may want to look into the magnesium thread on Reef Central. I can find the link if you need me to.
Basicaly, you need to find out where the nutrients are comming from. They are there, or your algae wouldn't be growing.
Battling algae is also one of the few times i would advocate using a UV filter to kill off the free floating spores and whatever little pieces get broken off, so they can't attach somewhere else.
