give some of stranges'goldfish pics

I found this blog while trying to find anything I could about frogs killing koi fish. We have a very large natural pond with 12 medium to large koi. Last spring for the first time we started to see tiny black fish in the pond, needless to say they were baby koi. We had a few hundred, many were eaten and many others just didn't make it. This spring, we were surprised to find that about 60 of the had made it through the winter. A few days ago, we began to hear loud noises from around the pond, it sounded like a bunch of turkeys. Well it turned out to be hundreds of small black frogs. I didn't mind until I saw one go after one of the baby koi and get on its back. I scared it off, but the koi was already dead. I began to watch them and they were hanging around where the koi tend to congregate, they float there as if they're dead and when a small koi swims by, they aggressively swim after it and and get on its back killing it in seconds. They were wiping out my entire small koi population, I even wondered if they possibly had some type of poison in them. So glad to hear that this is not unheard of!