Well, you *could* use lime, but it is somewhat of a pain the the butt to do. Adding lime to water results in "kalkwasser" which is used to maintain Ca levels in marine aquaria. However, to do this properly, you need to add the lime, mix and let the cloudy bits settle out. The cloudy material is the insoluble calcium carbonate. Then the clear, calcium rich portion is decanted off. This has to be done as soon as possible after it settles, because the kalkwasser will react with air to form more carbonates. However, I don't think it's worth the trouble, and for sure is not as potent as calcium chloride.
Generally, Ca only needs to be adjusted once or twice a season, unless you get a LOT of rain (several feet worth). The cost for CaCl is worth it in time savings.
Oh, and please don't use ice melter. God only knows what's in that stuff, as it isn't designed for swimming in. Is your health worth it to save a few cents?
Michael
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