some basic questions first:
did you go through the whole N cycle in the beginning? [I didn't the first time around and it just prolonged the algae growth issue]
what else lives in the tank, specifically, and what/how much are you feeding?
what does your skim collection look like?
have you tested for phosphate?[ when changing/adding water, circulate the new mix in a bucket with a ph overnight to reduce it - most salt mixes have a good bit of phosphate as part of the manufactoring process, and it would add a good bit of $$ to the price if it were removed before it went in the bag.]
do you have a wavemaker to randomize the current from your ph's - to eliminate potential "dead spots"?
p.s THANKS for what you're doing "over there"!