Help with clearing up Cl Puck Etching

[Buggsw]

Never heard of a green color caused by calcium. That's a new one on me.

 

[VoR]

Well I don't think it was actually caused by the calcium, but I think it may have been more of the calcium building up and locking in green from algae :?:

The previous owner was not much for maintaining much of anything from what we've discovered