Used Seaclear Commercial Strength PO4 Remover for pools. My tank is 150G. I dosed 2.5 ml into 4l of RO water and dripped overnight into my large overflow before a 10 micron felt sock.
There is a good thread on reefcentral:
http://www.reefcentral.com/forums/sh....php?t=1474839
and a good article in coral magazine
http://www.coralmagazine-us.com/cont...ling-phosphate
Didn't sleep well that night but it took my PO4 down to .07 the next morning Then I put gfo back online. Saw no ill effects, no drop in alk and tangs breathing was normal (common side effect of overdosing or LC reaching DT). Personally would not want to use it regularly or long term.