Pacsack, I hold 2 Vents in a 12*12*18, and we were rather creative when we built the terrarium for the thumbs, and made sure there was enough room to roam vertically. Beside the environment, though, you must make sure you're willing to equip the terrarium accordingly, plant it, and maintain high humidity, which from what I read, you are already well equiped for. Oh, and culture fruit flies...Now all of this becomes quite easy when you really get into it...