The thing about gar is that they grow much larger, and therefore eat more, than any bass. I've heard time and again from fisheries biologists that a single flathead catfish can clean out a pond of a few acres because they eat not only smaller fish like bass do, but the larger bluegill, shellcracker, etc. as well as the largest bass in the lake, because they're big enough to. A gar could easily eat every fish in that pond. Not to mention, if it happened to be a female with eggs, you've just ruined the pond even if a few members of other species survive.

Some fish are more aggressive predators than bass; in years past I've stocked Northern Pike and Walleye into Southern ponds in which the bass were not controlling the sunfish, and the toothy critters did the trick. The pike in particular made a huge, almost immediate difference.