Wow capensis, that was fast. You must have seen the post within about a minute of me posting it to catch that . The sand is play sand. It's called something like "white landscaping sand," which I guess is a certain type of play sand. It has some silica in it so I don't know if I'd let my kid (if I had one [which I don't]) play in it! Anyway, it's a lot cleaner than the other run-of-the-mill play sand I get from the hardware store, and the pygmies aren't complaining. It's just a half-inch top coating, copied from nightsky. Underneath it's about 2:1 sandeat or thereabouts. I got all the plants and basically all the growing information from Marius Vid (mark.ca), so if you're reading this, thanks a lot!
EDIT: two of my letters ended up a smiley. I'll leave it to you to figure out what it says