I have used both phosguard and kent Marine Phosphate sponge. They both show effects of working, but the effects are evident in the first 24 hours, then they just work so so.
If you really want to get rid of it you will need to do the 50% water change probably weekly until it is lower.
I usually do 10 to 15 gallon water change weekly to bi weekly. Try to stick to the ten percent weekly rule.
I also used Sea chem Reef calcium, reef complete, and trace elements?(red label, the name escapes me?) At 2x the manufactures recommendation(per instructions of my LFS
) It really gave my coralline a boost. I am not sure if 2x is necessary though, it clouded the water and it seemed that my skimmer almost immediately was removing it. I have cut down to regular dose and am using Kent Coral vide instead of the red label now that coralline seems more established.
all in all, seaham is absolutely right, take your time, I have been working on my tank for a year and it is far from complete.
there is very little enjoyment in stressing over and worrying about your tank.