OK.. I need help with my Magnum 350. When I first got the Magnum, I was amazed of how it cleared up my tank vs. using UGF and/or external filters. I recently cleaned out the Mag by changing the filter, wiped out the rotor, and changing water. Since then I noticed that the flow of water comming out doesnt even move the bubble from the airstone, nor its ability to suck water down the tube into the filter. I only had this item for 4 months and now seems defective. What would you guys suggest to make it work like before?