Hi, I have two questions: I currently have a 55 gallon aquarium running an Eheim classic 2213 canister filter and an Marineland BIO-Wheel Penguin 350. I received the tank and filters from a friend so neither of them were brand new. The Eheim filter has been working well from the beginning but the Marineland filter made some noise. Yesterday I noticed the marineland filter making a very loud noise now. I took out the propeller and cleaned it off and re-inserted it and it continues to make the same loud noise. Iv'e kind of come to the conclusion that the filter may just be old and it needs replaced unless someone thinks I may be able to fix this issue by just ordering a new propeller? 1. Can I replace the Marineland filter while keeping the Eheim filter without causing some type of cycle? Could I toss the bio wheels in the tank and let them float since that is where most of the BB is? 2. If I do by a new HOB filter which do you recommend? I have read some great reviews on both the AquaClear 70 (300) and the Fluval C4. Anyone have a preference of one over the other? Or should I stick with Marineland and buy another BIO-Wheel? All help and recommendations are greatly appreciated!