Matching Daily Calcium Dosing to Alkalinity Dosing

[Arringar]

The title of this thread may not be the best representation of the question I have, but what I really want to seek opinion on can't be easily conveyed in just a few words. That being said, I apologize if it later seems misleading.

Like many people, I dose a larger amount of Alk at particular times of day. Many people dose Alk at night in an effort to mitigate pH drops. (This is pretty much a useless practice in my observation.) I dose a much larger amount of Alk during the day when it is being actively taken up and then dose a much smaller amount at night. My Alk is tested twice daily, once just before the lights turn on and again just before they turn off. There is no question for me that this method maintains Alk in a way that minimizes the daily swing (to <0.3dKH) in my tank.

In contrast to this, I have always maintained calcium by dosing the full amount over a 24 hour period. Testing calcium multiple times daily has never shown a dramatic swing as it does with alkalinity but it does drop slightly (~10-20ppm) at the end of the photo-period as compared to when testing prior. Some may look at this and say 20ppm is not a small drop, but when compared to a ~1dKH daily alkalinity swing when dosing both over 24 hours I personally see it as a minimal change.

Currently my ESV 2-part dosing is as follows:

Alkalinity: 7dKH

55mL during the day (matched to photo-period)
20mL at night

Calcium: 440ppm

70mL over 24 hours


My question is: Is there any benefit or perhaps more aptly, is there significant enough benefit to change my calcium dosing to mirror the Alk dosing schedule laid out above? Obviously it would be very difficult to measure those benefits in terms of "does it benefit the animals", so what I'd really like to know is; could it potentially have a negative effect on ionic balance if not dosed similarly?

 

[Jonify]

I would say yes, technically, it matters, because the availability of calcium and alkalinity, relative to your pH, determines the rate of calcification and coral growth, but not on a scale you could ever observe running your current levels. So no, as long as you're replacing both over a daily period, your levels should remain fairly stable, and it doesn't matter if you're dosing them together, or a few hours apart--nor whether you did it all at once, or over several periods throughout the day. Replacing total consumption in a day is what most people shoot for, with good results.

The only situations where it would matter is if you were running 1) super low major element levels (slower growth if you bottomed-out one of the major elements between doses) or 2) super high major element levels (abiotic precipitation which could make it more difficult to keep your levels stable or measure actual coral uptake). Even so, it is unlikely you'd notice an appreciable observable difference in these cases.

 

[Randy Holmes-Farley Verified Community Expert]

My question is: Is there any benefit or perhaps more aptly, is there significant enough benefit to change my calcium dosing to mirror the Alk dosing schedule laid out above? Obviously it would be very difficult to measure those benefits in terms of "does it benefit the animals", so what I'd really like to know is; could it potentially have a negative effect on ionic balance if not dosed similarly?

No. As you note, the percentage change to calcium is always far, far smaller than alkalinity, and calcium is rarely a limiting factor to calcification anyway, and so the exact calcium dosing regimen is not critical.