Thank you both for your replies. I think I will rather get the heat cable/tape then. About the disinfection - I have already bought this
Wipe Out 1
GOOD.
I don't know how to translate hardware cloth into my language, but I guess I know what I'm looking for.

Is is sufficient though? If there isn't any of this cloth on the bottom of the tank, there won't be no air circulation. Regarding to my physics textbook, the gecko's farts will go up, but there will be no fresh air coming inside from the bottom. I hope you understand me
hardware "cloth" = metal screen
A glass tank has no ventilation/screen on the lower sides. The "hardware cloth" or screen is actually a grid (like graph paper), but metal. That would cover the top of the aquarium and provide enough ventilation.
- Cut it a little wider and a little longer than the opening.
- Bend the edges down to form a lip.
- Your tank is only 30 cm high. I think that will be enough air flow.
I'm not sure if my home is dry, but in the tank there is about 40% humidity at the moment, so I guess that is ok. And I read the post No.7 and I will do as you say. I will use the towels though. It is rather embarrasing, considering that I have lots of carnivorous plants, but I have no sphagnum moss and local gardening shop has none either.
40% humidity is good for leopard geckos.
You have really pretty vivarium

Although it would look much better with some coconut fiber substrate. You are not a fan of it? I heard they can poop it when they accidently eat it.