So I'm setting up a 75 gallon FW
tank, it came with an Emperor 400 filter, which is probably enough for my tank, but I also found my old Penguin Bio Wheel 200 laying around, so I was going to use that as well. I opened it up and saw that it was completely empty, no filter cartridges in it. It does however, have 2 slots but it looks to me like the slots are shaped slightly different. Am I supposed to use 2 filters in the BioWheel 200 or is the second slot for something completely different? ? Anyone have any ideas, I'm clueless lol.