Well, mine (all 6 of them) are still in a growout tank. I haven't added any to my main tank yet. They're all around 7-9 inches, I think.
Here's spec's:
55g
78-79F (stays pretty hot in the room)
pH 7.4-7.5 (just straight tap with prime)
Filter: Penguin 350
Tankmates: 2 bluegill (about 3.5"), 2 green sunfish (about 3.5"), 1 sun catfish (about 5").
I also have a decent size clump of floating plants in there to provide a little cover.
Mine are doing pretty ok. They're starting to figure out when I move up to the tank, I'm probably going to be dropping in feeders. However, they are still fairly skittish. If I move up to fast, they pretty much all startle and bolt to the farthest point in the tank.
However, they seem to have absolutely no issues with their current tankmates. The bluegull and sunfish stay pretty active, and with their dominance posturing, you'd think they could startle the gar easily, but they don't.
So far mine have only eaten feeders, even though I've been trying freeze dried krill and tilapia fillet as well. One of the gar did mouth a piece of tilapia for about 2 minutes, but he eventually spit it out. I'm hoping that over the next couple weeks, they'll start taking tilapia or krill, so that I can stop buying so many feeders.