I've had mine for a couple
fo years now in a 12 gallon nanocube.... It's too small but he'll be upgraded to a 24 when the volitan moves out. 24 gallons in plenty big. The 12 gallon isn't actually too small in regards to living space.... it's too small for hiding spaces. There's just no where to go when he gets nervous .
So, 24g is my vote.