Mag/Ca/Alkalinity Fluctuation Curiosity Question

[gklossner0916]

Curiosity question related to the core reef tank parameters.

Background 11 gal tank with approx 5.5 gal of water after subtracting for rock ect. I have not performed at water change in 1.5 weeks and also fed very little since only one fire shrimp in tank. I have soft and sps coral in tank. Acropora, birds nest, candy cane, 2 rocordia, pulsing xena, Kenya tree.

Question is: my mag/Ca levels have not changed in 5 days. Still 1440ppm and 440ppm respectively. Alk has dropped from 10.5 to 8.5 in that range. Trying to understand why Mag/Ca have not changed.

Thoughts?

 

[lil sumpin]

What are you using to test these? I think the alk drop is pretty typical over the course of a week. I see very similar trends in my 14g tank (approx 12g of water) and rarely ever see Ca dip more than 10-20ppm within the that time frame.

 

[Randy Holmes-Farley Verified Community Expert]

Curiosity question related to the core reef tank parameters.

Background 11 gal tank with approx 5.5 gal of water after subtracting for rock ect. I have not performed at water change in 1.5 weeks and also fed very little since only one fire shrimp in tank. I have soft and sps coral in tank. Acropora, birds nest, candy cane, 2 rocordia, pulsing xena, Kenya tree.

Question is: my mag/Ca levels have not changed in 5 days. Still 1440ppm and 440ppm respectively. Alk has dropped from 10.5 to 8.5 in that range. Trying to understand why Mag/Ca have not changed.

Thoughts?

Alkalinity can be consumed or added in ways that do not involve calcium (such as water changes or increasing, declining or dosing nitrate), but the more likely answer is that you just cannot reliably detect the expected drop in calcium of about 14 ppm and certainly cannot detect the 1 ppm drop in magnesium that is expected if corals or coralline algae are using all three to make skeletons. :)