Well, goldfish can give your fish parasites if they are left in the tank with your fish... If your fish consume them as quick as you put them in the tank, then your chances of disease from the feeders is decreased dramatically(depending on the fish you're feeding them to). Not only do goldfish carry disease(with all live food you risk disease), but they have a lot of fat in them. When I use live feeders, I prefer rosies over goldfish(less fat but could still be diseased). I also quarintine the feeders for a week before I feed them off. All of this is just my opinion so --research-- and make your own conclusions.
Hope this helps!