i guess it all depends. if you use substrate, alot of people use hydroton clay balls for drainage. i've built my large viv with not too much planning, it turned out super sweet, but no draining system. i do plan on hooking up a MistKing in the near future and with all of the substrate i have, i dont think two 45 or even a minute spray a day would leak. if you have an all cage with a potted plant, than as most have stated, a drip pan is what is used.