depending on how much actual floor space there is, you could probably use it until the snake gets about 4ft. I have a few 25 T (tall) that I use for some of my yearlings and adults up to 3 ft. It won't give you as much floor space as 20 L or 25 L (longs) will, but you can utilize the height of the tank by putting vines or branches in there for them to climb or to use as a basking perch if you use a heat lamp. I find its better than a 20 long for some of my younger and smaller corns because they get good exercise from climbing plus I can only watch them do laps in a 20 L for so long...Younger corns seem to be vertically inclined than adults....I mean they seem to search up for things that are up, and adults seem to be happy on the ground. And its gives them a good way to burn off excess "young" energy.