Ahhh... there is a real possibility of calcium overdose in some situations, especially if excess D3 is provided as well.
When everything is working perfectly, and the tortoise is well-hydrated, etc., then yes, excess calcium is passed in the bowel movements. Otherwise it may contribute to calcium-based stones, overly brittle bones, overgrown structures, etc. Overdoses of D3 add to the problems by calcifying soft tissues, etc.
I have to disagree. Calcium can interfere with the absorption of other minerals, trace elements and certain fatty acids. Too much every day could lead to other mineral or elemental deficiencies. This is why I only use it twice a week in small amounts (coupled with a good varied diet). If I was rehabbing a tort with a calcium deficiency or something I might use it 4 times a week in a little larger quantity. Sometimes I'll use it more with egg laying females too.
Yup, you can overdose on calcium....not only does it block the absorption of other vital nutrients it can elevate blood flow (similiar to high blood pressure in humans)....just saying is all