I know it's a dumb question but if you only purchase fish and livestock from 2 or 3 local lfs's and your tank got hit with ich or velvet wouldn't the fish in their store show signs as well? Especially velvet, it seems like it would wipe them out as well. Or would it be hidden due to a larger filtration system? It doesn't make sense how someone can buy a fish at one, introduce it to their tanks and wham! But the lfs's fish look fine.