Bullfrogs in my pond are the food supply for the redtail hawk that visits. Fortunately, my pond is large enough the bullfrogs don’t take it over and eat the other frogs to the point they disappear. Hard to tell how big they are as they spend most their time hiding under the bridge like trolls.
At the moment, have green frogs, bullfrogs, gray tree frogs, pickerel frogs and tons of baby toads in the main pond. Now the smaller pond by the front of the house, has been taken over by a large male bullfrog. Only have native fish in there, so if he can catch them more power to him.