Fish tank fun

The kittens are entirely sure that I bought them a new toy! I took the fish tank from preschool home for the summer and the cats have not left it alone!! They are sure I brought them a snack, and they just have to figure out how to get it!! I am not kidding when I say they sit there for hours watching and circling the fish tank, trying to figure out how to get at the fish. They have found a small opening in the back where the filter goes in and they can get a drink, but can't quite get at the fish. At least not yet!