I bought a brand new tank from a saltwater fish store(100 gallon), and it has saltwater lights, This tank is freshwater and the water is always green! Phosphates are at 0, and I have to Emperor 400 power filters running and also I have PhosGuard in there. Water changes are done a lot! Especially now that it's so bad, in fact the other day I did it so the tank only had 6 inches of water left, and now it's all green again, is there any ideas? All help appreciated!