Of course you could always just buy healthy fish in the first place. I pass a LOT of things over at our LFS's because they are a mess. You gotta learn to 'see' those problems beneath the surface. And then you have to learn to acclimate the fish from the SG of 1.017 (local fish store and wholesaler SG) to your tank salinity without tearing up their mucous membranes. If you do it too fast, all those diseases held at bay in the diluted water will explode. It can't be done in an hour!!