Having both cats and fish I can sympathize with your loss and the guilt you must have over the whole thing. Unfortunately you have learned a lesson the hard way. Please do not blame kitty for what he did. He was only being a cat. Maybe at some future date you may have more fish and I am sure you will be more careful next time, making sure that your fish is well out of the way of kitty's reach. We have two very large tanks and thankfully they have glass tops and no one can get to the fish. Actually my cats just like to watch them through the front glass and no one is in danger.