I noticed that when I feed fish, a lot of food gets sucked into the filter before the fish can grab it. Today I wanted to treat my fish with some grindal worms, but instead of settling to the bottom, they were sucked into the filter in half a minute or so. It's both a waste of food and unnecessary pollution of the filter. I have two possible ideas to prevent it - one, put a coarse filter sponge on the intake, two, put a think pantyhose on it. However, wouldn't that undermine my whole point of getting external filter, as all the visible mulm would get stuck on whichever cover I put on it, instead of getting into the filter, and I'd need to clean that cover every few days?