I been have nitrate problem lately i have a 75 gallon reef ready tank.I have about 8 fishes and 14 corals living in my tank 3 shrimp a few crabs a feed them once a day i have a etss protein skimmer a sump tank and a aqua uv sterilizer ,i only use ro water but i still have to change about 10 gallon a week can anyone help with that .I also have 2 leather corals who doesn't seen to open up lately i have move them different times but haven't got no answer