120 gallon tank won't get hot enough

[Marvin12345]

I have just built a 4x2x2 (or 120 gallon)melamine tank for my dragon. I wanted to have everything set up before I brought my dragon home and it is all ready except for the heating. I have the zilla slimline desert 50uvb bulb at 125 F, a 40 watt incandescent light bulb at 160 F, and a 75 watt ceramic heat lamp that is 500+ F. Even when all of this has been running for an hour the tank's highest temperature is still only 82 F. The melamine board that the lamps are attached too on the ceiling is about 175 and would prefer if this temperature did not increase so the boards no not warp/melt the melamine. The UVB light and incandescent are on a scheduled turn on to represent daylight and the heat lamp is connected to a thermostat to turn on below 82 and turn off above 100. Should I also put a heat mat on the bottom of my cage? Not sure how else to heat the tank.

 

[Aaradimian]

Hi! In trying to figure out the question of heat for my own dragon, I found out from other posters that the ambient air temperature is not what you need to focus on, but the surface temp. of the basking area. Prior to learning this, I had a single visible lamp over the basking area of the old viv at close range, and it was way too hot.

The most accurate way to take temps appears to be an IR gun, which can be purchased at least here in the US for around $20. The air temperature of my setup runs at whatever the house thermostat is set for, but I have two visible spectrum flood lights, one over the basking spot to keep it at around 105* F and another over a rock that I keep somewhere around 100*F so that he has the option to stay warm after lights out for a while (until the rock cools). I'd recommend getting lights with a dimmer switch in the cord so you can just choose a fixed height for the lamp and then mess with output via the switch until you get temps just right. On mine, I have to adjust the height of the lamps, which is a pain. Also, there's a helpful guide somewhere on the site about how to use the IR gun properly.

 

[KarrieRee]

I have a Zen Habitat 120 gal tank and use a Exo Terro 100 watt basking bulb directly over Hiccups basking rock w/ a 100 watt heat emitter that sits in front of the tank same side as the Exo Terro - that side of the tank runs about 85 or so under the heat emitter and 105 or so on basking rock-- both are on top of the screen --
Karrie