do you know exactly what species of leopard it is? i know of a few commonly kept in aquariums and they need anywhere from 20-40 gallons for a single specimen. if i remember correctly, in another thread, you said it's in a 10 g tank. why not get a 55 and make an awesome vivarium habitat?
You could setup a pretty sweet paludarium for them. I still wouldn't mix species.
i was more talking about putting a few more of the leopard frogs but yeah it would be a really sweet tank. i love catching rana pipiens and taking pictures of them, they are beautiful. one of my favorite parts about spring is finding frogs and toads the size of your fingernail