I have this really nice aqueon filter which I've had for a few years. Its worked great until now. This morning it wasn't doing anything but humming. No water was flowing. It works full or empty, so i know the problem is not that it was empty or anything. I opened it up and it all looks clean and in order. Any advice here? I don't really want to go buy another filter, this one is only 2-3 years old. What should I do?