Hi all,
Been keeping my gunite pool on the low side for calcium, as I am afraid to coat my salt water chlorinator plates with a bunch of calcium, am I in danger of pulling calcium from the pool and damaging my walls ?

Gunite pool -1995
fc = 3
ta = 120
calcium = 80
ph = 7.2
CYA =0 [if you ever read "cyanurics-benefactor or bomb" you'll stay low as well]
I use Ben's test kit for these

If I need to add calcuim , can I use some other source[Home Depot] for calcium chloride/carbonate so I dont have to pay pool store prices ?
P.S Pool has some very hard white crusty stuff on tile from previous owner- I cant get it off , assume its calcium ?