Just today I noticed that the bottom piece of the tube on my AC powerhead, has some kind of white stuff on it. Should I leave it? Clean it? My cycle is now finishing off... There are currently 10 feeder fish in the tank. The tube I am talking about it the tube that sticks out onto the surface and sucks air. The piece that has white stuff is at the bottom piece where it connect to the power head. What should I do? What is it?