my gar are currently in a 55 by themselves growing out for the 310. My aren't real jumpy and dont bang the tank walls really at all so the whole "small gars small tank" thing is hit or miss. Mine are aprox. 5" I'd say, maybe slightly smaller and I havent had a problem yet. Good luck with them, they are awesome fish, but like what has been said already on here they need alot of room...all thats in my tank currently is two sword plants about 12" tall and they love to hang out in that when its lights on and they float right under the duckweed mat in the corners when the lights are off. I am having a bit of trouble getting them to take anything but feeders but I'm alright with that for now until they bulk up a bit. again, good luck! post pics!