I'm planning for when my marcianus reaches adult size (wont be long he's a right greedy guts).I need you'r advice,I'm thinking about getting a vivexotic http://www.vivexotic.co.uk/products.html.i would like to get him the on that measures 36"L X18"L X21"H but would that be to big for him?Or would the 36"X15"X16 be a better size for him?(I'm not 100% sure on the sex though)