Goldfish for food
I have purchased feeder goldfish that I deliberately picked out for markings or pretty tails. I live in Kansas and when the electricity kept going out in the winter storms, I would lose my temperamental tropical fish. So...just out of desperation to have an aquarium at all, I went to the carps and Kois (hence my handle "carplady"). I progressed to the better looking un-feeder fish at times, but you might be surprized to see what some of those feeder fish turn out to be, some are exquisite. They don't need heat, in fact they are better off in cool waters. They will eat snails (yes, snails are bacterial and virus carriers) but, mostly they are vegetarians, so my daughter and I collect pond greens from a local area, and will also feed them with several kinds of pond fish food, giving them a diverse food supply.
I agree with the person in this thread who implied that viruses are rampant, even to us, from anywhere. Some of your fish are bound to get sick and die, after all, humans do, it's ok, we'll have a stronger strain of fish, or you can look at it like this, you're forced to "go shopping", maybe you'll take that opportunity to try a different specie.