I have a 55 with a Whisper 60 and an emporer 400. I've had the tank set up for a year and change, have had the emporer in for 4 months, and everything is great. The thing is... my bio wheels have no biological growth on them. When I put the emp.'s in the tank, I packed the two empty filter containers with a lot of different stuff, smalll gravel, crushed coral, some carbon, some sponge filter (used in aquaclear). Is it possible all of the biological materials are being trapped here, and are therefore not forming on the bio wheels? Any other suggestions/comments?