Over the last few days the calcium and magnesium have been randomly increasing in my 30 gallon reef. I tested yesterday and parameters read calcium 485ppm, alkalinity 9.2 dKH, and magnesium was around 1600. Today the alkalinity 8.4 dKH and calcium 550. I’m testing with the Red Sea Foundation Pro kit. How are these parameters rising when I’m not adding any supplements or anything to the tank? My salt supply is Instant Ocean and salinity of 1.026.
Calcium and magnesium increasing?
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Randy Holmes-Farley
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Unless the salinity is rising (due to evaporation that you didn't replace), the rise in calcium and magnesium (if any) can only come from dosing or test error.
See that’s all I can think of also. I top off my tank daily and it maintains a salinity of 1.026. I used API test kits recently and added calcium and a buffer due to low levels (which was 9 days ago) then I proceeded with a waterchange 2 days after that due to testing error again with API. Which is when I purchased the Red Sea kit and over the last 7 days after the waterchange my levels have been going crazy.
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FWIW, the Red Sea magnesium kit seem prone to erroneous values.
Yeah I’ve read that. But what explains the alkalinity and calcium daily fluctuations? Could it be the previous dosing I done and it taking effect now? My tank is softie dominated with 1 LPS coral so it don’t fluctuate much if ever.
Randy Holmes-Farley
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It never takes more than a day for an additive to mix in and be detectable (think of it like food coloring added, how long would the tank take to look one color?).
In the absence of dosing, calcium and alkalinity only decline and do not rise on their own (barring things like water changes and some highly unusual situations which are not likely here, such as dosing nitrate that is adding alkalinity when it is consumed).
So "fluctuations" in those are likely test error as well (if you are not dosing).
Don't over-interpret day to day changes. Look to long term trends.
