Cleaning calcium build up

[IslandReefer]

The makers of CLR tout that their cleaner (reducer) is make from "natural products" and is food safe after a rinse....whatever that means. I often wondered about fish tanks though, because the stuff works like a hot damn, but I'm no guinee pig (read chicken )
.....I too use white vinager and elbow grease.
......If you let the coraline dry and turn white it comes off "easier"
Good luck