If you're considering a 30 gallon tank, you may also want to consider using a Rubbermaid container, or for a little more $$, a Vision or Animal Plastics (or Barr's or Boaphile) cage of the same dimensions - you'll have a much easier time regulating your snake's environment in something that doesn't have a screen top. Things like this are good to think about prior to purchasing an enclosure can save you quite a bit of $$ in the long run. If you purchase a cage that doesn't require a lot of modification to properly maintain the correct environment, chances are you won't have to spend money on accessories to make up for any heat or humidity loss that you may encounter with an aquarium. Also, the plastic herp cages are typically much lighter, practically unbreakable and made with a herp in mind.

Just food for thought...

K