Keep doing as you were Caper as it worked well for you. Me, I am lazy so don't clean them until I really really have to :lol:
I have had a hang on the back filter with a thick coating of fuzz over the outflow lip. Didn't impede the flow so I didn't worry about it. It only got cleaned when the sponge got so full of crud it pushed the lid off the top of the filter case :roll: