Its hard to get gar off live food while keeping five fingers, lol constantly wiggling Silverside in front his mouth is no fun, but until he gets atleast 6" he demands live food, I've had 4 gar, 3 barracuda and 3 knifefish which all with a lot of work acceptected Silverside and shrimp(clown,knives were the easiest) but I always feed them. Goldfish when I don't feel like risking my fingers, and raising fish on feeders is perfectly fine as long as you give them variety and supplements, your asking for trouble if you feed your fish just one thing. I've raised a yellow tail barracuda on goldfish from petco for 3 year. And no dieseses, as long as they eat them right away if don't think they can hurt your fish, but it is a risk