I am having the same problem. This year I seem have thousands more tadpoles than usual and cannot see the fish without a dozen or so tadpoles swimming after them. They are attaching to fish and eating their dorsal fins and the scales off their backs. The fish now have bare patches and no dorsal fins, just bones sticking up. It is definitely the tadpoles causing this due to there being so many of them and not enough food. I have removed three bucket fulls of tadpoles from the pond and now make sure that there is always plenty of fish food around the plants to keep the remaining tadpoles happy. The fish damage has now stopped but, of course, the bare patches are starting to get fungal growths. I have dosed the pond with Medifin and keeping watch. Next year we will remove the frogspawn to a local pond and just keep the newts and toads.

Jim