I am beginning construction of an outdoor enclosure for Ambystoma Macualta. it will be 4x4 feet and 15" tall. the enclosure will be 10" into the ground to allow them to burrow. the goal is to add a water source in the spring time and hopefully allow seasonal changes to initiate breeding. i have a few questions that im hoping people with outdoor enclosures can hep out answering them. first, what can i line the bottom with to prevent them from burrowing out? i was planning on putting galvanized rat wire on the bottom, no sure how well it would work. i considered pond liner, but didin't want the soil to become water logged. Also, how much space is needed for around 3 adult pairs? is a 4x4 foot enclosure overkill?