My cat always used to help too. As soon as the lid came off the tank that is. But i had this one really smart fish that would splash back and forth through the tank and get my cat soaked (and my carpet) so after a while the cat stopped caring.
Love those pics! Luckily my cats haven't taken much of an interest in my aquarium, except once when we had visitors one of my cats panicked and tried to jump in the tank....happily we had the cover closed.