[mangoandmimi]

Chinchilla sand is good yes, that or playsand, reptisand or similar. No 12cm across is too small in my opinion as they really enjoy more sand than that. I would give at least a quarter to a third of the cage as sand. Then you have room to place some hides in there too which they often like to use to bathe in an enclosed space. All my robos have shown more interest in the sand areas than burrowing areas but you do have to provide both.