Originally Posted by Taz
You're probably right & I've used most of my filter equipment far longer than dealer recommended (of course), although I understood the wheels had fine charcoal imbedded in the filter material, but i could have been misinformed & have never taken one apart (not sure if you could see it anyway). A friend of mine (who has an independant pet store with his wife - he does the fins/feathers, she does the furries) told me he just throws the wheels away because if they clog & stop there can be a problem with the filter overflowing out the back.
The Bio-Wheel itself, should never need to be thrown away, unless ripped or not functioning properly. Like I said, I've had the same bio-wheels for almost 3 years. Alot of companies and chain LFS tell you to replace them because they want to make money. If you are having problems with your biowheel not flowing through your pads properly....I'm guessing that the pads are clogged with debri and fish waste.
On my 20G, during my weekly pwc, I will "swish" the pads around in the dirty tank water to get all of the gunk off of them, and then place them right back in the filter chamber. If you try that and still find little to no water coming through the filter, I would dis-assemble it and clean the propeller and the intake tube.