when to test for Alk, calcium and magnesium

[Noodles_Jefferson]

This is a fairly simple question. my tank lights run from 2pm to midnight. When testing these parameters, does it make a difference if I test in the morning when the lights are off vs. in the evening when the lights are on and the corals are all blooming?

 

[CasperOe]

Not really, although if you want to trend it, try and test at the same time every day.

Depending on your dosing pattern, alkalinity may be higher in the morning before the lights come on as your coral will consume alkalinity during the day as part of the photosynthesis..

From a practical point of view though, I wouldn't put too many thoughts into it though - but I am sure you will get a ton of different opinions here..

I test:
Alk - 00, 06, 12 and 18
Ca - 00, 12
Mg 06, 18

Automated..

 

[Randy Holmes-Farley Verified Community Expert]

This is a fairly simple question. my tank lights run from 2pm to midnight. When testing these parameters, does it make a difference if I test in the morning when the lights are off vs. in the evening when the lights are on and the corals are all blooming?

Doesn’t matter when you test, and I recommend never testing magnesium as the result is so likely to be inaccurate that it causes more trouble than it is worth.

Calcium won’t change much over the course of 24 h, but will decline a bit between dosing.

Alk can change quite a bit in 24 h. I’d measure just before you next want to dose it.

 

[Noodles_Jefferson]

Doesn’t matter when you test, and I recommend never testing magnesium as the result is so likely to be inaccurate that it causes more trouble than it is worth.

Calcium won’t change much over the course of 24 h, but will decline a bit between dosing.

Alk can change quite a bit in 24 h. I’d measure just before you next want to dose it.

I've found that as long as my calcium and alk are right I hardly ever need to add much mag.