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Originally Posted by chiahead Actually this is not true. |
Um, yes it is. It's an ion exchange resin that exchanges Ca2+ and Mg2+ ions with Na+ ions. The sodium chloride recharges the resin. Unless (as you mentioned) it's a potassium softener, then it exchanges them for K+ ions.
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Originally Posted by RTR I though that GH only read divalent ions, not the monovalent such as Na+, K+ |
It does, but the monovalent ions can skew the results if there are enough of them. Lamotte states in their hardness kit instructions to dilute a saltwater sample by 92.25%. Personally, I used to maintain a .10% salt level in my tank (1000 ppm NaCl). I recently stopped. As I did weekly 40% water changes and the NaCl dropped, I noticed that I was having to add more Ca and Mg to get the same test kit readings. It ended up I had to add 84%
more Ca and Mg to remineralize my RO/DI water and get the same test kit results
after NaCl levels dropped to negligible levels.
I also need to correct myself regarding my statement that I don't know of any kits that test only for calcium. Lamotte makes one, test kit #3609. It includes inhibitors that stop ions other than Calcium from registering.