I took Claire's advice and hit the aquarium shop down the street. It pays to support locally-owned businesses these days. Turns out they had the perfect size aquarium set-up on sale! (They also happened to have two baby weiner dogs on the premises; weiner dog puppies are much nicer than the adult Weiner. Adult weiners are cranky and very barky. But I digress.) The lid appears to be cat proof as well. We'll see what happens when actual fish are added this weekend. If I'm especially clever, I'll upload a pic or two.