Calcium rising

[raultsu]

I tested my calcium last week and the it was at 454. I stopped dosing calcium that day and only dosed Alk. next day Ca was 475 what the heck. tested again next day Ca was 499 what the heck. 2 days later 456. 2 days later 462. Im only dosing Alk and have tested with Hanna and salifert test kits. im using Brightwell Calcium and Alkalinity. Any ideas on what could be causing this?

 

[Randy Holmes-Farley Verified Community Expert]

Either test error or changes in salinity by evaporation. A 3% increase in salinity due to evaporation (3 gallons from 100 gallons water volume) will boost calcium from 450 to 464 ppm.

Calcium does not rise on its own (unless you top off with tap water with has a lot of calcium in it).