I have a cf300 canister filter that I have had for about two years i have really liked the preformance of this filter until now, for some reason the output flow has decreased down to a trickle. I contacted the site where I purchased it from and they said it could be the impller . Any body have any other thoughts about what could be causing the flow problem. It has gotten regular cleanings and the tubes were clean when I checked them. I have my daughters Ehiem 2234 on the tank right now.