No, black headeds are terrestrial. Some experts recommend a 1.5-2m square enclosures for adult black headeds. If you're going to make it higher, then you could keep some smaller arboreal snakes in it, such as young coastals and murray darlings, bredlis, jungles or green tree pythons (if you have the money, and depending on what you make it out of). If you leave it the size it is now, and the enclosure is to last the snake to adulthood, then a member of the Antaresia group (spotteds, stimsons, childrens or a couple of pygmies).