Sounds like you're using the wrong type of light bulb or lamp if you're looking for light rather than heat out of your light. The UTH should be large enough to heat the tank air and substrate to 80F on its own. Only the ones from Ultratherm and Flukers have enough power (wattage?) to do this, and only these brands can be insulated , which helps you get your temps up without causing a fire. If your UTH is not getting the tank to 80F on its own, and it is mounted on the back of the tank above the level of the substrate, then it's either the wrong brand or is too small. Or it may need to be insulated. Most of the time, the UTH will need to cover the majority (2/3 to 3/4) of the back of your tank, in order to get the heating required.wrswrs2 wrote:I have a UTH not a heat lamp. I just mean when I turn the light to the tank on it heats it up into the 80s but the humidity goes downhill. So now I end up misting a couple times a day
For recommendations on lighting, see the lighting care guide post. viewtopic.php?f=25&t=92543
Sounds as if you got ahold of some lighting that puts out heat, and that's why your substrate is drying out. I think you should try a cooler light. Maybe fluorescent or LED? But it also sounds like you have something going on with your UTH, because it should be keeping your tank at a stable 80F all on its own.
I'm assuming you're using the standard 5:1 playsand/Eco-earth substrate moistened with marine saltwater until sandcastle consistency. I'm also assuming you have a glass aquarium with a glass lid (or mesh lid covered in plastic wrap) to keep humidity in your tank. I'm also assuming at least 6" deep substrate. If any of my assumptions are wrong, these could be contributing factors to your tank behavior.