While I'm not sure I'd call my aquarium fish 'intelligent' they definitely have their own personalities and unique behaviors. Amusingly the saltwater ones seem much more animated than the freshwater ones, but a lot of that may have been due to breeding/the environment the freshwater ones come from.
I've got a pair of clownfish that are very entertaining and tend to play together, and then a paranoid purple tang that freaks out and hides whenever anything happens near the tank.
But.. yeah, PETA is a bunch of idiots.