4 X 2 ??? will this just be a temporary thing ???
For a female blue I would advise a 6 X 3 at the very least .
My enclosure is about 20 inch high and I just about get away with it but 75% of it is plexi glass so to not make Alpha feel enclosed.
https://www.tegutalk.com/threads/whoop-whoop-finally-done-alphas-new-forever-home.19379/