Algae problem

[VP Clown]

I am suffering from some type of macro algae, it is brown dusty and covering my GSP to a point that the polyps are not coming out. It comes off with a blasting with a turkey baster, it is like a brown dust.
Nitrates are 5 and phosphate 0.25, both checked at LFS. Salinity 35ppt, pH8.2 (evening) Calcium 440 mag 1220
The tank is a Red Sea Max and is 15 months old I do approx 10% w/c weekly. I have put in bag of purigen, 3 weeks ago, bag of seagel 2 weeks ago and now a bag of rowaphos, last weekend. The skimmer is working well. lights T5 compacts 8 hours a day
Never had any real problems before so i suppose had to happen,
Any ideas, is it cyano or beginings of hair?? :mad::mad:Help

Andy

[VP Clown]

Hi have had no replies, and since originally posting I have done 2 x 20% water changes, no change.
I have noticed now that my branching hammer looks to be deflated, previously it was always inflated, is it normal for them to deflate or is this a sign of a problem?? It has really done well and grown around 3 / 4 heads since getting it this time last year.

The tank just doesn't look right,
Another question is that - how long do snails last, I haven't topped up my CUC since introducing the originals 15 months ago,
Any suggestions or help most appreciated
I'm also looking to getting rid of a reasonably large Leather (sarcophyton) sp if anyones got room its free to any one who wants
Andy