Can anyone actually confirm their frogs actively attack fish by swimming after them? What I've seen with green frogs, is they are ambushers that use a sit and wait strategy and believe bull frogs are the same? At night, my local greens would hop around the pond's perimeter, looking for insects from what I could tell. During the day, anything IN the water they ignored unless it was on the surface or bounced on a lily pad they were hiding under. I have MANY minnows now and those get ignored (one swam too close to a green frog and it actually fled from the minnow despite being an adult frog)
I've seen many comments about frogs eating things, but have yet to see any actually chase IN the water, so don't think they'd make a good in-water predator? They will chase or make an effort out of the water including jumping up to get worms tossed in high grasses. But I've tossed worms at frogs in 1-2" of water where they were sitting, and they always struggle as they can't strike it.