Solutions What Type Of Solutions Work To Clean Hard Water Stains, Yet Won't Harm My Clearwater Septic System?

What type of solutions work to clean hard water stains, yet won't harm my clearwater septic system? - solutions

I tried everything on the hard water stains on the toilet, but will be of solutions that we use on our guard. I can not bleach or chemicals, extremely hard, and it kills the "bugs" in our Clearwater septic system. Has anyone tested cleaning solutions and less rough on the hard water stains? Thank you!