I have an aquaclear 500 that I converted to a mini fuge. The main problem with not doing a full change and just cleaning the pads is that you disturb all the "crud" that sinks to the bottom of the aquaclear. When you pull the basket out, it creates a suction that pulls all the "crud" out as well, and then the particles get pushed back in your tank. I think it would be reasonable to alternate doing a through rinse once a week on these units.