Because mourning geckos are nocturnal, they don’t need special lighting in their terrarium. However, I hold a firm belief that even dim lighting is beneficial for nocturnal species to regulate their circadian rhythm (natural day/night cycle). Furthermore, if you have live plants in your mourning gecko terrarium, keeping fluorescent or LED lights on for 12 hours/day will encourage healthy growth.
Again, because mourning geckos are nocturnal, UVB lighting is not required. However, it may be helpful at 2% or 5% strength. Wild mourning geckos are commonly observed basking and being otherwise active during the day, especially in the morning.
Mourning geckos thrive between 77-82°F (25-27.5°C), with a night drop down to 72°F (22°C).
That is the data I’ve found from my research. However, in my experience and the experience of other mourning gecko keepers, they seem to do just fine at room temperature between 72-77°F (22-25°C).
A basking spot between 77-82°F (25-27.5°C) seems to be the best compromise in this situation. You can create a basking spot with a 60w incandescent bulb in a small dome fixture at the top of the enclosure. This will create warmer temperatures at the top and cooler temperatures at the bottom. This gives the geckos a temperature gradient with which they can regulate their internal temperature as needed, and facilitates better ventilation as well.
Temperatures should never exceed 85°F (29°)! Your mourning geckos will get heat stroke and die. You can keep track of both temperatures and humidity with the Zilla Digital Thermometer-Hygrometer. Measure your basking spot temps with pinpoint precision by using a temperature gun like the Etekcity Lasergrip 774.
Mourning geckos are healthiest in 60-70% ambient humidity with higher levels up to 80-90% daily. You can create and maintain these levels by misting 1-2x daily, depending on how well ventilated your enclosure is. However, make sure that the enclosure dries to 50-60% before misting again, as mold and fungus will start to grow otherwise.
Mist heavily enough to create droplets all over the terrarium. Mourning geckos don’t drink from water dishes, so misting keeps them from getting dehydrated.
Do not use distilled, softened, or even filtered water for misting! Tap water (assuming that it’s safe for humans to drink) contains minerals vital to your gecko’s health. Yes, this means you’ll have to clean up water spots, but it’s worth it. Here’s why.
PRO TIP: Remove hard water spots with a cotton ball soaked in lemon juice (old spots might take a little elbow grease!).