1. Any knife fish
2. Blacktip/bull sharks
3. Piranhas (to many people think they will be easy care.
4. Glofish. I was at Wal-Mart the other day and when I was in the fish department. Some people were going to buy some glofish for there sons birthday because they looked cool. Then the were looking at bowls to put them in. They never bought it because of the expense.
5. Feeder fish as pets. In my lfs
. They sell comets for 28˘ a piece. Ive know people to biy them and use them as party favors. Only sell them as feeders.
6. Common plecos. Too many people ghink they will stay cute, and eat poop.
7. Fiddler crabs. I all most bought one before I knew they needed to surface.
8. Bala Shark. They need huge tanks. From my experience, ive seen a 6.5" bala cramped in a 55. Not pretty.
9. Large gourmamies. These are usually cramped in a 10 gallon by a uneducated fish person.
10. Fish bowls. I know its not a fish but its so wrong it belongs here.