im afraid they carry parasites with them internally, which eats them inside out, also you dont know what dieases were in the wholesale tanks. im using antibiotics, what you said is very true, but dont you think medication would work better when fish is stronger? when they are sick might be to late for medication to work? i look at this stuff like how humans do so in the medical feild. when someone has treatable tumors and treatable deadly dieases, you dont wait till you get sicker eh? but then like you said there is a chance they might be clean and i would be medicating them while they are heathy which makes them go unheathy heh, but after reading so many diease problems i rather work on the fishes before it's to late ^^ better safe then sorry