I'm using whisper filters on tanks with DIY CO2. As long as the water level in
the tanks is kept high there's not that much turbulance. I used to run the CO2
air hose into the filter intake, with very good results, but I now use a really
cheap ($4 - $6) diffuser, the Rena Micro Bubbler from www.petsolutions.com.
This is even more effectiveand lots quieter. However, the diffuser tends to
leak where the end caps attach to the media tube, but a little silicon glue
fixes that.