I have a turboflotor multi 1000 protein skimmer which until recently was working fairly well. Now when I plug it in the pump (oceanrunner 2500) seems to be "burping" but not putting out the pressure to fill the chamber with bubbles. I have tried cleaning the pump, and taking it apart. All parts seem to be in good shape but when I put it back together it doesn't seem to work. The skimmer itself has some slime in it which I can't get a brush to. Any thoughts. Thanks in advance.