dont use treated lumber!! i had an iguana for about 5 years and i built his cage. but the reson i know not to is i work at a hardware store and i know that the chemicals used to treat wood is actually pretty toxic. so much so, that they warn not to use around gardens cause it will leech said chemicals into the soil and is very carcinogenic (i know its spelled wrong too tired to type it right lol) same applies to using it for picnic tables and such. get a good outdoor paint and just paint any part of the inside of it that will be in contact with his water or if its going to be very humid just paint the entire inside. sorry for the story just no need to risk a pet...