They can survive in the wild and take pretty much any US fish just shy of southern Apex predators, they are very, hardy very aggressive, and eat a lot of food. In addition to being illegal they can run up to $10 a day to feed so they won't eat tank mates.
http://www.aquaticcommunity.com/predatory/effects.php
http://www.aquaticcommunity.com/predatory/effects.php