20g x-high is a great sie. It has the footprint of a 10g but is twice as tall. My 6" long male is in a 10g, but I have a 20 x high for him to move into. To tell you the truth hough he seems alright to me in the 10 for now. BTW, your gonna have alot of fun with a crestie, they are a great herp and very friendly.