[LindaB]

Hi

I havent experienced this myself, even though I kept koi for some years, but I do know of it.

Your frog is simply desperate to mate - anything will do lol

They can damage the eyes of koi and they will sometims even latch on to the gills.

I wonder if you could put a very fine net tightly around your pond to try and prevent them getting in? Thats the only thing I can think of to try and avoid serious damage to your fish.