hmm.. yeah I would wonder about the side effects of such a high fat diet, particularly of mammalian nature upon them. particularly a diet thats not varied at all. Though I suppose there is some data to back doing this. Other then I/m fairly confident powdered milk replacement for cattle is dirt cheap compared to pellet costs. and stored properly likely has 2 to 3x the shelf life. I just have a hard time believeing the fish are getting all the proper nutrients they need to grow properly. I'de have concerns w/ fat around the heart or other organs, and an overall shorter life span in general. I'm not sure I'de complain as it sounds like a realistsic business adjustment to make, many koi farmers particularly in japan (and other places) take great pride in their fish and provide exceptional care to their animals. I'de be cautious investing in a "milk fed" koi.. but I can't exactly argue with the practice.