I have housed a baby in a 20 long, you just have to fill it up with plants and stuff! You can also use crumpled newspaper to fill up the empty space. You need two identical hides, one on the cool side and one on the warm side. The hides should be tight fitting and have one small opening. Only feed once every 5 days. If he refuses then wait 5 days before trying again. I would feed live until it has eaten several meals before attempting frozen. Babies like to hunt for the food! Cover the sides and top of the tank for added security. If they don't feel safe then they won't eat! You need digital thermostats to read belly temps or the warm(90-94) and on the cool(80-84) side! The ambient(air) temp has to be at least 75 degrees! It your temps aren't right then they can't digest their meals so they won't eat! No handling until it eats 3 or 4 times then only once a week to start! No handling until after 48 hours of a feeding! To thaw out a mouse, put it in a ziplock bag and put that in a sink full of warm(not too hot) water for an hour or so then take it out and give the head a blast from a hair dryer for a minute or two. The head should be a little warmer than the rest of the body so it can eat the head first! Good luck! Pics of your setup would help us better!