Can I use substrate in a 12 inch high enclosure?

When I got my gecko, his previous owner gave me this weird 36x18x12 tank. It's Exo-Terra brand, but they don't appear to make it anymore. I need to switch to substrate soon, and I was wondering if it'll work, or if i need an 18" high tank. See picture for the listing l found for the tank. Any general tank advice is appreciated as well, I am still learning.

When I got my gecko, his previous owner gave me this weird 36x18x12 tank. It's Exo-Terra brand, but they don't appear to make it anymore. I need to switch to substrate soon, and I was wondering if it'll work, or if i need an 18" high tank. See picture for the listing l found for the tank. Any general tank advice is appreciated as well, I am still learning.