A warm welcome to Geckos Unlimited!
I recommend covering
half the ground with a heat mat. For a 20 long (30 x 12 x 12 inches) that means an 11 x 17 inch heat mat. It's not overkill. Your leo will have more heated floor space to explore.
For your vivarium (90 x 45 x 45 cm -- 36” x 18” x 18”) I recommend 39 feet of Flexwatt heat cables attached with aluminum foil tape. If you configure the red cables on the right side (alternating long, then shorter, loops), I think it allows for a more gradual gradient from hot to cool. The first 6 feet of the cables are not heated.
Be sure to read the directions.
Do the red cables:
Example only:
Be sure to get a thermostat to control the heat cables.
A leopard gecko needs a 12" high enclosure. Consider building some ramps. If you find the heat cables are not enough, add a Ceramic Heat Emitter overhead.
Here's a temperature guide for all leopard geckos as measured by the probe of a digital thermometer
- 88-92 F (31.1-33.3 C) ground temperature right underneath a leo's warm dry hide
- no greater than 82ish F (27.8ish C) air temperature - 4 inches above ground on the warm end
- no greater than 75 F (23.9 C) air temperature - 4 inches above ground on the cool end
Leave the UTH on 24/7. At night turn off overhead lighting/heating (~12 hours on and ~12 hours off) unless ambient room temperatures drop lower than 67ish*F (19.4*C).