Hello all, I've require assistance from you all before and your help is appreciative. But for the past several month (actually since the summer) my tank has not been doing so good. Only some corals are doing badly. I have hairy mushroom room corals that are doing well they just keep getting bigger, but some of my common mushrooms are shrinking. I can't manage to keep any hard coral alive except one. I have a open brain that doe’s well but any other type of had coral dyes within 60days a slow death. Most will start to close up after two weeks to a month. I have a 90-gallon tank with 160 pd. or rock 70% Florida and 30% Fuji I also have 30 pd. of live sand and 30 of agrinite sand. I have 4 VH0 3 tircramatic and 1 blue and the bulbs were replaced two months ago. I have a 20-gallon sump with bio-balls, a Berlin protein skimmer and sand bed filter. I'm running 6 power heads for water movement. This tank has been established for about 1.5 years. I notice that there is some brown algae growth and the macro alga grows at a very slow rate. I detected some silicates but I don't what is consider to be a dangerous level also my phosphates are 0.05. I put silicate and Phosphate remover in a canister filter yesterday. Nitrates, Nitrites, Ammonia, Copper are all 0. I change 40 gallons a month (20gal biweekly). I have tow tangs 3 clown fish 50 hermits and 50 snails.15 types of mushrooms 15 polyps 1 bubble coral 1 brain and some misc. soft coral.