Hi I have a 600 internal pump which came with my Rio 180 Tank I have had the tank running for 8 weeks with no problems. But now my pump is making a loud vibrating noise, I have took the pump apart but as I am new to this I do not really know what I am looking for, impeller all looks good, I have been told that the magnet maybe the problem, but I would appreciate any help you could give me into sorting my headache out. Many Thanks in advance. ihmix