I have a Top Fin sponge filter in my tank and it's making a loud humming noise. It started after only a few days of having it. I'm using my sponge filter along with a 5-15 gallon air pump for a 10 gallon tank. If I lift the filter off the tank floor a few inches then the sound will stop, but it starts again the closer it gets to being set back down. Anyone familiar with this sort of sound from a sponge filter?