I have been rehabilitating Am's for about 25 years (no, I'm not that old, I just started VERY young). In my rehab tanks, what I've found works best is the same soil that dear ol' toad was living in when you found him, thats right "Yard Dirt". It's easy to refresh, readily excessable, and the price is spot-on (FREEBIE). As far as heat goes, it seems like Toados Americanos likes things on the cool side (65-75 degrees). There is a growing colony of them here ("I am the TOAD-KING, I feed everything!) and I've seen them begging for food on my patio when it's as cold as 50 degrees. I keep my house relatively warm so I don't use any heat source at all. I put about 4" of good ol' "Yard Dirt" in the bottom of the enclosure, along with some dried leaves and a big peice of bark. For water, I mist the cage at night when Toadasaurus is on the rampage (feedin' time). These critters don't need much water. I mist just enough to get said citter wet and keep his substrate damp. If you mist them too much they will let you know by giving you a dirty look from beneath their piece of bark. I have brought many of these little crusty varmints back from the brink in these little hospitals. They seem to respond well to ugliness, just keep it clean (Hah! clean dirt!) and change his "Yard Dirt" every now and then. I even dig up a little sod complete with grass to pretty it up a bit, but they don't seem to care (ingrates). Good luck with your toad. If you love him, he will love you right back(Toads show their love by peeing on you).
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How to get your wife to like toads; 1.Get a male toad. 2.Get him to hug your wifes wrist (amplexus). 3. Tickle him so he chirps in protest. 4.Say "Awww, he likes you". Note; Make sure he pees first or you may receive bodily harm during this procedure.