Technically you could use it. However I strongly recommend not using it. Sand can still cause compaction at any age. And really. Is looking at sand worth, have you gecko dieing, painfully from compaction, compared to looking at carpet, and being healthy? It is a personal decision though. That is just how I think of it.
Yeah, better than woodchips. But even though better, no really all that great. Here I copied and pasted this, from the care sheet I had written.
Substance
After you have purchased the enclosure you need to pick a suitable substance. There are quite a few to choose from, including, a bare floor, newspaper, cage carpet, tile, packing paper, play sand, and calci-sand. Here are the pros, and cons of each.
Bare Floor
The problem with bare floor caging is that it is simple ugly. The benefits are that it is very easy to heat, and you don’t have to replace anything, and it is easy to disinfect.
Newspaper/Packing Paper/Cage Carpeting
The drawbacks of these are that they are all ugly (I actually like how cage carpeting looks). However they are very easy to clean, and replace (Cage Carpeting can be washed). All of these also allow for easy heating.
Tile
Tile flooring is about the same as a bare floor, except it looks better.
Sand/Calci-sand
The problems with sand are that there is a chance of impaction and it is harder to heat. The benefits are that it is easy to clean, can be replaced, and is inexpensive. Don’t ever use sand with geckos under 5” though, as there is a major risk of impaction, I recommend never using sand at all, no matter the size or age of the gecko.
I would not reccomend any loose substrate for leos. Stick with something safe like paper towels,newspaper,tiles,reptile carpet,or for something natural,slate rock..