supplementing tank

[burnsie2005]

So I was told that I should be supplementing my tank with calcium and iodine to aid in the growth of the shells for my snails and to aid in molting for my crabs.
I'm just wondering if this is true and if most of you do it. I've had quite a few snails and hermit crabs die. I don't know if this is why.
Any feedback is appreciated.

 

[allterr]

Do you have a cal test kit? You really shouldnt add anything you cant test for....
And most elements occur naturally in the water when you do waterchanges, so adding anything may not be necessary as long as you have a good water change schedule down....