Just to clarify a tiny bit more on the bio-wheel, as I also have one...it is acceptable to rinse this (in used tank water), but only advisable in a very-much so established tank when it may become so covered in new/dead-decaying bacterial colonies/other gunk that it actually doesn't rotate well or at all anymore (it could also be the bearings which you can just wipe off with a paper towel--that is those little purple grooves the wheel sits on), and the only instance this will probably happen in is if your tank is about 6 mos established or much more. My tank is coming up on 10 months and my wheel is still going strong.