Unfortunately, bullfrogs can get very big.
And they are the most aquatic of all North American
frogs so while they will hunt away from the pond
(ours used to hunt mice at night under the bird
feeder) they will always head back to the pond
and there will be the fish.

Greenfrogs also get big and don't make the same
kind of dent into the fish population.
If you are not sure of exactly what your frog is,
bullfrogs have a ridge of skin that starts behind
the eye and curves around the eardrum. Greenfrog's
ridge doesn't curve and goes down the back.

kathy