Hey guys so I need help with a 75g tank of mine. I have 2 marineland 400's on it. The tank water is green. I have tried a week long blackout period, and I have done large water changes as well. It will clear up for a day or so but shortly after is back to turning green. I cannot get this water to clear up. Last water check I did I had 0 ammonia 0 nitrite and 5-10 nitrate. I am running out of ideas.