I have 5 Penguin filters, 2-330's, 1-300, 2-125's. I have found they are very sensitive to intake restrictions-I clean the tubes,strainers and impellers weekly during water change time. This only takes a few minutes with a round brush and quickly restores water flow. If the filter pads get plugged up the water will back flow @ the intake and the wheels will stop too. Snails seem to love the bio-wheels and get stuck in there all the time, and will climb into the housing, breeding in there and lead to the filters clogging up as well.