That's true, and that's why Lepisosteus platostomus (shortnose gar) "only" hits 2' in aquariums. In the wild, they get to close to 3'. If your tank is 30" wide or more, go for a shortnose... as xrtg said, they are fantastic fish. None of them are very aggressive though, so if you're looking for an aggressive fish, gars don't fit the bill. Generally the only species that's remotely aggressive is the alligator gar, and even they aren't too bad.