Well, you can catch lots of diseases, but most common ones are species only. A lot use animals as carriers, but the animal doesn't really have the disease/parasite. But I highly doubt that the fish will give diseases to the frogs. They can't get ich or any other common fish diseases.
Actually, I'm pretty sure some funguses and bacterial infections can be passed between them... I think I'll ask the frog forum.
Robert Falcon Scott - Red salamander HM plakat
Passed on- Friedrich "Freedy"
Four African Dwarf Frogs - Dorkus, Sporkus, Baron(ess), and Bubbles!