You have to remove the dead worms and gunk that they produce. That is their poop and other dead matter. You can give them flake foods etc, nothing much. Just don't overfeed. I typically don't feed my worms. I just leave them as they are since anything leftover after 4 days to a week I just clear out. Some people use a sponge bed or a fine filter pad for the worms, which also works.