I only replace mine when the BIO-Wheel no longer spins.
I kind feel that this should be a sticky!!
Also, if you have a Regent Aqua-Tech, you can modify a BIO-Wheel for it. If you do, you should remove the Bio-Fiber if your Aqua Tech has it.
Products Needed: Bio-Wheel
Bio-Wheel Bearings
Bio-Wheel Bracket
Lid (Optional, but reduces evaporation)
Aqua-Tech 5 and 5-15 - Bio Wheel Mini
Aqua-Tech 10 and 10-20 - Bio Wheel 125
Aqua-Tech 20 and 20-40 - Bio-Wheel 170
Aqua Tech 30 and 30-60 - Bio-Wheel 330
Hop This Helps Everyone!!
P.S. They don't sell cartridges for Millennium Filters at walmart. The Whisper Medium fist Primo and Millennium 1000, but the regular size/large does NOT fit the Millennium 2000 or 3000!