You might want to dust the mice and fish with a calcium dust. Use a dust that has no phosphorus in it. Repcal or reptocalcium are good choices. Also (and I'm not an expert on it) feed the mice and fish less often. Finally, I've heard that goldfish are too fatty to be a good food for a horned frog. Feed them crickets instead or , if you want to feed them fish, use rosy reds instead. Good luck!