ADF love plants to hide in or behind, they also like other hiding spots like a cave or similar things to hide in. They feel save in it. When they go for air they often like to hide for a short while after or in it.
Substrate can be important if they would get it inside when eating from a dish this might be prevented. but some of the food might still get out of the dish so I would still be careful with what to use. I do not know Tahitian Moon sand so really can not say anything about it but like said, sift sand substrate like play sand. I would not use colored substrate like the orange or purple stuff they sell in pet-shops.