Alk cusumption is varying week to week

[Luno]

So I had a doser malfunction a month ago or maybe a bit more. And my tank was not getting dosed alk. Dropped from 7.7-8 to around 5, lost one coral out of the issue. I've since brought my alk slowly back up to 7.4-7.7 depending on when I test. And everything was fine.

My tank usually has a consumption of around 1dkh of alk per day. So I dose according to this. Same dosing but doing it manually till I grab a new doser. Now one week my alk at the end of the week for my water change will be at 6.7, the next week my alk will be at 8.3. Using the same salt water, and volume of water for water change each week.

My tests kits are accurate (Red Sea, salifert) as I test my tank, another tank and the freshly mixed up salt water all
Accurate to what each other test kit says and what the new mixed up salt water should be. So tests kits shouldn't be the problem.

Now my question, I have quiet a few years of reefing under my belt. I have never seen demand of alk fluctuate on a weekly basis without changing the tank inhabitants (adding or removing inhabitants) I did loose the one coral and expected a small consumption change but not to have wierd high and low swings week to week.

Any ideas?

 

[Randy Holmes-Farley Verified Community Expert]

Tank demand for calcium and alkalinity depends on many factors, some of which may vary. One of those is tank pH which can vary with the CO2 level in your home air. So the number of people in your home, opening of windows, and even how cold and windy it is outside can impact indoor CO2 levels and hence demand.

Of course, measuring the same number of hours after dosing, lighting schedule length and timing in relation to measuring, etc., all would impact the value.

 

[Luno]

Tank demand for calcium and alkalinity depends on many factors, some of which may vary. One of those is tank pH which can vary with the CO2 level in your home air. So the number of people in your home, opening of windows, and even how cold and windy it is outside can impact indoor CO2 levels and hence demand.

Of course, measuring the same number of hours after dosing, lighting schedule length and timing in relation to measuring, etc., all would impact the value.

Was waiting for the master to chime in. The thing is I don't see any reason for ph, oxygen and carbon dioxide to change at all. No change in lighting, the only thing is my refugium cheato is a little full needs to be culled back. And the dosing instead of 10 times a day is 3. Surely that wouldn't be the difference of the alk. But it also isn't changing between say the week it was in the 7's and the week it was in the 8's

 

[Luno]

I think that's what I'm struggling to wrap my head around what made it consume 1dkh almost more one week and 1dkh less one week. With no real changes outside of the tank. If it was the change in dosing or the cheato you'd expect it to be consistent in one direction not more one week and less the next

 

[Randy Holmes-Farley Verified Community Expert]

I can't be sure what it might be from,whether test issues, or some real effect. Many of the processes in our tanks are coupled in ways that are not always obvious. Maybe nutrients or some trace element has gotten to the point where they are limiting coral growth, nitrate levels changing can impact alkalinity, etc.