I don't think so. I have heard a bullfrog hiding in the waterfall of my pond, but have never seen him. I think he moved on because I haven't heard him in a while. My four large comets are still there. They are probably 8" long.
The frog could of had a field day on my mollies. They reproduce like crazy.
Bullfrogs are not really adept at catching fish, you'll be fine, especially at the sizes you mention.
The pond at our ranch has HUNDREDS of bullfrogs right now, and hundreds upon hundreds of tadpols changing into them.