Very good points from both of you Diana and Raven, especially the importance of a q-tank.
I'm constantly harping that you're not saving any money or doing yourself or your tanks any favors by buying the slightly less expensive "puppy mill" type fish that so many of the chain stores carry.
In most cases a private breeder is
a superior source for fish, but there are many variables there too that should be taken into consideration. Where did his originating fish come from? It's always possible that they came from the same source as where we are buying our unscreened fish. Is he just pumping them out to sell without proper care and conditioning in less than perfect conditions? Those examples aren't normally the case, but it can happen too.
With fish like Guppies that are so line bred to get certain traits like specialized fins and color, it has really affected their hardiness, resistance and health.
I do still buy fish from our local store to support them, and they will leave them in the bag for me when they come in so they have one less acclimation and tank of water to go through. I trust our store because they have very strict requirements for the quality and health of the fish they carry, and it shows. I also quarantine for quite a long period, even though they look fine, just to be sure.
If I remember right, I thought once you've had TB in a tank, you need to sterilize the entire tank and all of it's components (including isolating the remaining fish in their own tank) or you'll never completely get rid of it, and could pass it along to future inhabitants. I'm sure if that's true, it has greatly contributed to the spread of it.
Diana, you made a good point about the vet actually testing the fish for TB. That is the only true way to diagnose many fish ailments, and properly treat them for it, if applicable.
And I also agree, it's no fun to watch any fish die or even not live up to it's full potential, so some of those simple precautions will greatly improve the whole aquatic picture.