Hello! I am not expecting any brilliant revelations from this forum, so if any are forthcoming I will be grateful as well as surprised. I am 63 and I have been taking care of pools of all types since I was a child, although never professionally. Currently, I have an 18,000 gallon inground, diamond-coat, outdoor, unenclosed modified kidney with coconut palms, sable palms, tibuchina and geiger trees within leaf and flower dropping range. My skimmer works overtime. My pool service recently QUIT on me claiming my pool was too hard to keep clean, so I have taken over the task of maintaining it with mostly success, but my tests are consistently indicating I need to add 10 to 20 lbs. of calcium hardener every month. This seems excessive. The price at the local Pinch-A-Penny is outrageous for a 20 lb bag of calcium carbonate. Is there any difference between that and the calcium carbonate marketed for ice and snow melt? It's about 1/4 the price and it would make sense for me to use that and save quite a lot of money. Any thoughts?