I've never kept white lipped tree frogs, but I do know they get very big - even bigger than Whites, so a 30 vert is perhaps the minimum size for a pair. Go larger if possible. They do have similar habitat preferences as Whites, but behaviorally tend to be more skittish - so more cover maybe advisable. Agree with Michelle on the live plants and false bottom. Check some of the sticky threads under the vivariums discussion part of this forum for lots more information. Paper towels are easier to clean, but not if you want live plants. Otherwise, the substrate cover can be anything from moss to leaf litter, and will not be an impaction risk if you don't let their prey run around in the tank and instead, use a bowl to feed them.