Hi, Did you know that they now make the biowheels by themselves so that you can hook them up to the return for almost any under the tank cannister filter? I love the Marineland biowheels, but am not very fond of the Magnum filters or the eclipse filters or and of their other filters with their biowheels.....but I love the fact that they now sell the biowheels to hook up to the return to your tank for any other brand......I love these. I use these instead of a wet dry for my tank and the nitrates are always zero! Lesley