i used to work at a crematory that had a contract with all of the petco stores in dc/md/nova.
some of those stores would send a 50lb. bag of dead animals (which an overpowering fish odor) weekly.
in general, i prefer to avoid buying livestock at the big chain stores, not to say i never do, but it's not my first choice. i am guilty of buying feeders at petco regularly, however. and $1/gallon tanks.
a couple of interesting anecdotes of petco visits:
i bought my red-belly pacu at the burke location. he was in a corner tank all by himself, with no price or label. i asked the clerk how much the pacu was, and got a puzzled look. i pointed him out and the guy said "oh, we thought that was a silver dollar, but he was picking on the other silver dollars so we moved him."
another time, at the fairfax location, they had "red terrors". i know, doubtful they were real festae for $5. they were in a tank with some oscars, dempseys, etc. so i decided to get one, and the clerk gave me the usual spiel: how big is your tank? what kind of fish do you have? do you know this gets big? blah blah blah....then she asked me "which one is the red terror?":lol:
makes me glad there's the availability of private sales and still a handful of independently-owned shops around!