the bigger the better but that may do. You will need to keep them dry and cold over winter. I use hollow logs or PVC tubing and cover the bottom in damp peat moss, you won't see them much for three months but the females will come out in spring full of spawn (can be seen as black speckles through their skin in front of their hind legs, at this time you need to keep the males away from them but in sight of them (over eager males can cause females to drop their spawn before it's ready) then by late spring/early summer introduce one male to females and keep the other close so they can hear each other. Use heated water and best on on night when you have a huge storm with thunder and heaps of rain. eggs take 24 hours to hatch if viable.