While wild-caught can be an okay thing, this isn't always the case. More than a few species have become endangered due to the over-collection in the wild. This happened to celestial pearl danio until someone figured out how to breed them. It is currently happening to the beautiful redline barb (
Puntius denisonii) although efforts are being made to breed them. Over-collection in the wild coupled with habitat degradation is causing their numbers to plummet. Another incident were wild-caught fish are bad is with the blue-eyed panaque, a rare loricariid catfish. They are found in an area of South America controlled by drug lords; if any wild fish is exported from that area, the proceeds go to these drug cartels (
read more). So the lesson to this little rant is some wild caught fish like cardinal tetra are good, but others are bad. Research before you buy.