What I do is...
Every other water change (once every couple of weeks), I dissamble the pump/filter. I put the filter in one bucket of water, while I clean the impeller & casing with a toothbrush (the only thing this toothbrush is used for). I don't clean it thoroughly. Just get the gunge out of the intake, impeller bits and various nooks and carnnies. When I am done with that, I take the casing & pump out of the water, and rinse the sponge in both buckets. Then I reassemble everything and put it back in the aquarium. I also have a nylon stocking over my pump/filter. That's there to keep fry out of it, but it also reduces the gunge that gets into the filter. That, however, also need rinsing, and occasionally washing.
p.s. do *not* replace the filter unless you absolutely have to, and then, 'start' the new filters with material from the old one. I found out the hard way that much of the tank ecology system lives in that filter!