I'm new to this myself. I have uth (heat mat) under his hot side on a thermostat and a che (ceramic heat bulb) on a thermostat over the tank for ambiant heat because it is pretty cool in my house. My tank is roughly the same size as yours. I did add a second water dish on the hot side as the che really dries out that side of the tank quickly. I use two digital thermometer/hygrometer meters...one on each side. As long as you keep a thermostat on your heat mat and check your temps at least once a day (I use a heat gun for spot checking) he should be good. I would put the heat mat under his hot spot though because they don't do much for heating the air but do great for belly heat. Also, if you struggle with humidity and temps, if you have a screen too, you can cover most of it with something like aluminum foil. It helps a lot. Just make sure you leave enough open for air to circulate. As I said I'm no expert, I've had my guy for about a month,but this set up is working for me.

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