nothing will happen i have kept these with fish before never got one to stay alive more than a week (when i used to buy from petsmart) and every time one died a fish would peck at it,they never suffered any ill effects
Unless you have only very small peacefull fish in your tank and you make some important arangements for the frogs well being such as lowering the water level a bit and having lots of plants, this is a species that really should be kept in its own tank.
My 2 live in a planted tank with a breeding group of cherry shrimp, they are very slow to feed and I probably wouldn't put them in a standard comm tank. They seem to be doing well as they have bred but I haven't raised any of the tadpoles as they are very difficult to keep alive.
Just wanted to add that I have three of these that I have had for about two years, great pets, BUT......mine are in a 2 1/2 gallon species tank with lots of cover, a heater, and a Palm Azoo hang on filter and that is all. They do NOT like lots of water movement like a powerful filter or the noise from an undergravel filter powered by air. Also they seem to be almost blind and IMHO would have an almost impossible time fighting with even guppies for food.
The CLAWED FROGS are much more aggressive and would fair better in a community tank envirenment......until of course they ate the fish.
So IMO, you want aquarium frogs.....think species tank.