Hi there, I have a Needlenose Gar, he's pretty cool. He's about 6-7", 8" at the most. He eates pearch and walleye(small-medium), that I use for feeders. I know he'd eat anything that could fit in his mouth. And believe me, his mouth is bigger, much bigger then it looks. He's not aggressive at all though. He stays at the top of my tank. As a matter of fact, I just put him in my 120gal. with my Aro. Kinda nervous about that, but so far so good. As long as my Aro is fed, I don't think he even cares about him.
But just remember that the Gar can eat something that is thicker then his own body. (pretty cool to see him eat.)
IMO, I wouldn't put him in a community tank, but that's just me. Plus I like more aggressive, big fish.
Good luck to ya...
Jeanna