Do calcium levels fluctuate?

stanleo · Mar 8, 2025

My tank hasn't been using up calcium I don't think. I have had a Trident for over a month and it has been consistent on reading Alk and Mag but calcium jumps all over the place. One test it will be 450 and 12 hours later it will be 470. I haven't been dosing because I can't figure out how much calcium my tank is using if it is using any. The Red Sea kit shows 450 consistently. I have calibrated the Trident twice now. Is something wrong with it or are they a waste of money or are the fluctuations normal? I sent out an ICP test to see how accurate the Trident is, waiting for the results.

Uncle99 · Mar 8, 2025

450 versus 470ppm is not a great flux for hobby grade testing. That includes Trident.

I stopped using my Trident and sold it as I seemed to use up, a ton of time fiddling with it.

If Alk is being used, CA must be getting used.

The variance in testing is super minor, it would not have got any attention from me.

Randy Holmes-Farley · Mar 8, 2025

It could be test error, or a salinity change, but calcium does not rise aside from salinity changes unless it is dosed.

stanleo · Mar 8, 2025

Randy Holmes-Farley said:
It could be test error, or a salinity change, but calcium does not rise aside from salinity changes unless it is dosed.

When the test ran at midnight, it said Cal was 448, when it just ran at noon, it says 464. I did not dose. But, now that you said salinity changes I am looking and it does look like when the salinity is lower at 33.5 ppt the calcium is below 450 and when the salinity is is up to 33.7 the calcium reads at over 450. I do auto water changes of 1.5gal/day with a DOS and the new water is around 34 ppt. What does that tell you? Is there something wrong with the trident and I just shouldn't trust it for calcium?

BryanM · Mar 8, 2025

It sounds like when your salinity is higher, calc is higher, and that sounds like what one would expect to see generally. Though that .2 change of salinity isn't all that much.

Why does your salinity fluctuate? Skimmer maybe?

edsbeaker · Apr 12, 2025

On my trident, my calcium jumps around too. I try to watch the trend and not the daily ups and downs. Over a couple of days, if the graph is showing an upward trend, dose less, if it is declining, dose more. If it’s going up and down, but the average seems to be about the same, you are good.