Ditto what RR & Biggen said. What type of water are you using (RO
or tap water)? Also, what kind of salt mix? Almost all salt mixes, when properly mixed with RO
water will have a calcium level of somewhere between 350 - 420. Given this, water changes would bring high calcium levels back in check.
If you are using tap water, this could be an issue - I have seem some well water which tested extremely high for ca