Ok, I'm sorry, I forget to give details each time, I was trying to hurry. It is a 75gl tank, I do 15gl water changes every other week. And I am worried about my corals. I have a piece of live rock that has 3 freebe mushroom corals on it, I think that they are all dead. I just saw one of my other mushrooms looking weird. The center "dot" seemed to have purged out. I thought something was sitting on it but I watched as it went back in itself. It was a pink flowery looking thing comming out of the center. From what I have read, nitrate at 25 is border-line deadly.