Thank you for the time. My tank is 2 years old and I have a protein skimmer that is on the back top of my tank. Thinking about that I now notice that coraline has grown into the intake strainer for lack of a better word. I dont know if I am getting as much water into the skimmer. My skimmer is producing skum though. I have really cut down on my feeding and even added a rabbit fish. I think that is what they call him but he doesnt touch the stuff.