Here is the lay out. Nitrite = 0 nitrate =80 - 100 (here is the problem) ammonia = 0 phosphate = in tank 1.0 / fresh from ro/di = 0 (tested twice each way) DKh=7 PH = 8.3 My tank is 65 gallon with live rock and the following fish. has been established for over 1 year. 2 clowns (1.5") 1 six line wrasse (1") 1 fox face (3.5") 1 blue hippo tang (2") several snails and blue leg hermit crabs, 1 cleaner shrimp, 2 emerald crabs and one sand sifting star fish. I feed them one to two times a day about one cube of home made food. the cubes are about a 1/2" square if that helps. I am making a fresh batch of saltwater now to do a 30 - 40% change. What do you think is causing this problem with Nitrate? Why is the in tank phosphate 1.0 but fresh from the RO/DI it is 0? any help is appreciated!