xander here. what dimentions is the 125g? small gars do best in smaller grow out tanks, at that size a 2x1x1 would be better. the 125 should be fine for a good while(can only tell you specifically when you let us know the dimentions of the tank) provided there is some good cover around for them and no large/aggressive/skittish tankmates.
nvm im getting a 100 gal. thats 60"x20"x22" next weekend and i'll get gars from my lfs they just have them under some stupid name none of them even know what they actually are so i'll take advantage =)
the 100 should be fine for a while
heck probably forever but cant guarentee that(way too many things that can chage this)
nice tank
trying to track one down for cheap but yeah right