High calcium can lead to clouding of the water and if the pH gets too high, along with the calcium from over use, it can put an unsightly scale on your liner and ruin it. Bleach, which has salt (sodium hypochlorate) adds a minimal amount of salt to the water unlike Cal Hypo, Tri Chlor and Di Chlor and is the safest of all because it doesn't have additives that will drive the water parameters out of whack.
That's not exactly true, in that sod hypo has a very high pH, circa 11-13, so if you don't add acid at the time you add sod hypo you will drive the pH up, because the sod hypo has a high acid demand. This increased pH then slows down the effect of the added chlorine, because of the inverse pH/chlorine relationship. Rule of thumb is for every jug (20 pints) of sod hypo added, also add a pint of acid. Obviously this only applies if the pH is correct before the addition of the sod hypo. If the pH is out then the amount of acid needs to be adjusted accordingly.
