In one of the videos you see Sepp throwing something into the water and the fishing rising to the surface to eat it. But ... Sepp takes great pride in not feeding the fish - instead he creates fish food habitat.
He pointed out that the people making the video brought the fish food and asked him to feed it to the fish so there can be something more interesting to put on video.
Further, he pointed out that most of that pelleted fish food that is used for most aquaculture is made from the dead animals that were often extremely medicated in their last days in an attempt to keep them from dying. It even includes euthanized pets (cats/dogs/horses/etc.)
boy am I glad I read this! I was thinking of purchasing some fish food just for fun but I would actually like to eat some fish out of our pond and don't want to be throwing nasty stuff in the water. I thought there were some tough regulations regarding using euthanized animals for feedstuffs but maybe the regs are looser for fish food.