I know most epoepl start them out in a 6-12 q tub until about 500 grams or so then move up to next size.

Now I personally have had great success just going with a straight 40 qt tub (when I can find them when can't a 34 qt tub) cause by thetime I add some junk to clutter it up and every thing they feel safe enough and eat pretty good. ( i then slowly remove the items until there is noting left as long as they keep eating unti lthe tubs got just a a water bowl and a hide ( if they fit into it )