hi I was wondering what is the calcium substance that you put on a tortoises food before it eats it
thanks

Hiya,

Nutrobal is a good supplement. It should be put on food every day or every other day. As it contains vitamin D£ you do have to be careful not to put too much on the food as tortoises can overdose on oral vitamin D3. It should be used at a ratio of 1 pinch per kilo of tortoise. So if your tortoise is smll, not very much.
You can use a light dusting of limestone flour every other day and a cuttlefish can be added so your tortoise(s) can self-regulate it's calcium intake.

HTH
Darren