Hi all, I am currently running two emperor 400s in my 75 gallon freshwater. right now one of the filters is just using back to back standard blue padded filter pads with carbon bits inside. the other filter has the first line of filtration as the standard filter pad, and then i have filled the biomedia cartridges with some ceramic rings and other small bio rock pieces and a few bio balls in the mix. Am i using these filters correctly? should i be using the biomedia cartidges on both filters, or are the biowheels enough.