Yep...vinegar works great. Whatever you use, though, be sure to rinse well and let air dry before putting the contents and snake back in.

If you have hard water troubles, I would seriously consider buying some bottled water for your misting and such. I remember the water we had in San Antonio...omg, that stuff would leave a layer of cement on the inside of a tank if I misted with it every day! It'd be well worth the expense and trouble to switch to bottled water.