I just put mine in a 40 gallon and he is about…. maybe 2 feet? A friend who breeds snakes said it was too soon for me to put it in a 40 gallon. but I put LOTS of decorations in to make it feel smaller. He said it was fine since i put so much stuff in it. I have suction cup leaves covering 3 walls, 2 hides (one big one small) sticks, and plants, and 2 water dishes, and a skull. So the more you place in the tank, the sooner you can move him.