Depending on the ratio of the mix you do it can hold humidity really well or you can create a dry environment depending on what you are keeping. I don't use a drainage layer myself. If you are using a heat mat for your snake then don't do 5 inches over that as the heat won't make it through. I had to thin it out in my snake cage over the heat section...for my lizards they use bulbs so depth isn't an issue. I use springtails with my lizards but haven't decided if I wanted to make that jump or not with the snake. The plants will need some form of light to grow well.