i don't know much fish that do that...but that's because i only keep small community fish. only if you plan on getting oscars or something should u worry. small bottom feeders like cories don't do much except turn over a few pieces to look for food. the reason its bad is because
a)it could kick up quite a lot of nutrients which will lead to algae blooms
b)it could kick up quite a bit of fish poop which can lead to an ammonia spike