I have an 18x18x24 exo tera terrarium for my 3 Whites tree frogs. I use eco earth for the substrate and I have a large piece of drift wood and some fake plants/vines and a piece of bark covered cork as my background. I have a Zoo med hygrotherm and I currently use a fogger to keep the humidity around 69% and I use a heat lamp to control the heat. It has worked pretty good until now. The past two days I've noticed that even though I have the heat on in my house set to 70 degrees, the tank is only getting up to about 73 with one heat lamp. I've added an additional lamp to amp up the heat and right now it's at 77 degrees. With the additional heat lamp my humidity has now tanked and was at 56%. I'm assuming I have to get a UTH. My question is how big does it need to be and where on the tank should it be put? When I had my Exo-tera 12x12x18, I had a small UTH that I attached to the side of the tank. I never really felt like it did the job.

On another note, Skitter has been acting different the past few days and I don't know if it's the whole heat/humidity problem. A few times a day I will find him sitting in his water bowl for over an hour. Normally the water bowl is something he just passes through. Yesterday I caught him sleeping in it and took him out and put him on a leaf. He's eating normal, and I think he's pooping normal too because there was some in the bowl with him this morning and he was the only one in there. I picked him up for an inspection and his coloring looks normal, there was some redness on his legs but I think it was just from him trying to escape my grip.