Fantastic - and i will definately be building some stuff with lego!
I've got both playsand and coir in mine. one third coir at the heat mat end(helps humidity) separated from the sand with a tray of shells and a tray of sphagnum...stops one sub dragging into the other.
I've just noticed 'Textured Protein' on there, which is presumably the same as plain soya mince. Soy and soy products are on the edible foods list posted elsewhere. My boys have been eating it happily, what's the score?