Does alkalinity vary throughout the day?

[blueoverbrown]

I'm getting inconsistent alkalinity readings and it has me wondering if alkalinity can vary throughout the day like pH does? Or does any alkalinity drop just mean that the kalkwasser I've added has been consumed?

 

[Pod_01]

I'm getting inconsistent alkalinity readings and it has me wondering if alkalinity can vary throughout the day like pH does? Or does any alkalinity drop just mean that the kalkwasser I've added has been consumed?

Yes it will…
As evaporation and ATO top up change salinity your Alk will change.
As coral grow and consume Alk during day you get a dip and the dosing brings it back up.
Testing has its own variability so you may be seeing test variations when testing frequently.

I have not seen alk flat during the day…

 

[Randy Holmes-Farley Verified Community Expert]

I don’t think that any change except a steady decline is real. Salinity changes are too small to detect in one day.

 

[bryce.martin]

I don’t think that any change except a steady decline is real. Salinity changes are too small to detect in one day.

Im in the same boat, one day last week I had a surge in ALK reading from my GHL. Steady at 9.0-9.2 and then all of a sudden jumped to 10.2 for around 4 tests then the next day dropped right back down to 9.0 steady for about 5 days now. Tanks do weird things.

 

[Reef Jedi]

Yes it can change through out the day. That is why it’s recommended to test Alk at the same time each day. This will lead to more consistent readings. Are you adding manually, auto or trying to find your drop?

 

[Randy Holmes-Farley Verified Community Expert]

Im in the same boat, one day last week I had a surge in ALK reading from my GHL. Steady at 9.0-9.2 and then all of a sudden jumped to 10.2 for around 4 tests then the next day dropped right back down to 9.0 steady for about 5 days now. Tanks do weird things.

Are you dosing alk? Demand can rise and fall for many reasons, and if fixed dosing alk, the values will rise and fall.

But without dosing, alk generally cannot rise and fall day to day.

 

[Randy Holmes-Farley Verified Community Expert]

Yes it can change through out the day. That is why it’s recommended to test Alk at the same time each day. This will lead to more consistent readings. Are you adding manually, auto or trying to find your drop?

That only applies if dosing. Without dosing, alk does not rise and fall on a daily basis.

 

[zheka757]

Mine is on auto dose for every 30 minutes, but you can see the levels goes up and down from 4 tests a day, I have noticed the trend all alkalinity goes down in the evening/ or night just before lights go out, this is usually where my ph is highest

 

[bryce.martin]

Are you dosing alk? Demand can rise and fall for many reasons, and if fixed dosing alk, the values will rise and fall.

But without dosing, alk generally cannot rise and fall day to day.

Dosing ESV 2 part, first test I just eghhhh at the number, 2nd time it raised flags, 3rd time I then checked calibration. Everything was dosing fine, it was off by 0.1mL which is normal for my dosing heads.

 

[Randy Holmes-Farley Verified Community Expert]

Mine is on auto dose for every 30 minutes, but you can see the levels goes up and down from 4 tests a day, I have noticed the trend all alkalinity goes down in the evening/ or night just before lights go out, this is usually where my ph is highest

Which, if real, is just a timing mismatch between demand and dosing.

 

[Randy Holmes-Farley Verified Community Expert]

Dosing ESV 2 part, first test I just eghhhh at the number, 2nd time it raised flags, 3rd time I then checked calibration. Everything was dosing fine, it was off by 0.1mL which is normal for my dosing heads.

As noted above, when dosing, a timing mismatch with demand will make alk rise and fall.

 

[zheka757]

Which, if real, is just a timing mismatch between demand and dosing.

Maybe this picture can show better results, I should add temperature is at its highest point also during this time. I'm using your sodium hydroxide solution at 10 ml every 30 minutes. And its 100% guaranteed that my midnight test is going to be lower then my 6p.m. test

 

[Randy Holmes-Farley Verified Community Expert]

Maybe this picture can show better results, I should add temperature is at its highest point also during this time. I'm using your sodium hydroxide solution at 10 ml every 30 minutes. And its 100% guaranteed that my midnight test is going to be lower then my 6p.m. test

When are you dosing?

There’s no substantial mechanism for alk to rise rapidly except by dosing, and I’d suggest that testing is not perfect. Don’t try to interpret small changes. :)

 

[zheka757]

When are you dosing?

There’s no substantial mechanism for alk to rise rapidly except by dosing, and I’d suggest that testing is not perfect. Don’t try to interpret small changes. :)

How is it interpretation? It's just a fact with ph going up so is consumption of alkalinity. My ph is highest in the evening, and my alkalinity is always drops slightly towards the end of the day.
My doser is set to dose 10ml every 30 minutes for with no breaks through the day. This means the amount i dose is no different at any given time of the day or night.

 

[Randy Holmes-Farley Verified Community Expert]

I don’t understand the question about interpretation. Maybe if I just say “don’t try to come up with reasons for things that may only be testing variability/accuracy issues” it would be more clear.

I am frequently asked to explain things that fit that description because folks assume testing values are perfect.

 

[zheka757]

Randy, ether im not getting you, or you not getting my statements. All I saying is, alk consumption very through the day in my system, im seeing it as a result in my testing trends day in and day out, I dont belive it is to be a mistake in testing, as I see a same results. While ph goes up, my consumption of alkalinity increases and that same 10ml is not enough to keep my alk at same (prefered) level, but same 10ml of dosing is more the enough to cause alkalinity to actually go up slightly.
I asked the very same question a while back and you responded same way

 

[Randy Holmes-Farley Verified Community Expert]

I do not disagree that alk consumption varies through the day, and seems to typically be highest during the light period.

We do not really know if that is because of the light itself, or because that is when pH also peaks. :)

The op was asking if alk varied through the day, and my point is just that, without dosing, it does not vary the way pH does, going up and down, and typically just declines. If dosing is added to that scenario, and if dosing does not exactly match the timing of the alk demand, then alk can vary up and down.

 

[VintageReefer]

If not dosing alk it will decline but it is not at a steady rate. Some periods of the day you will have faster consumption than others. And other periods you may have no consumption. So yes, it varies in that the rate of consumption varies. It won’t go up on its own

If dosing x ml every 4 hours, and you test every 4 hours, you are adding a constant, but the consumption is variable. Then, if some tests show an alk increase, it’s because the prior 4 hour span had little or no consumption. Overall it should work out if the daily consumption is matched by an appropriate daily dose

 

[zheka757]

If not dosing alk it will decline but it is not at a steady rate. Some periods of the day you will have faster consumption than others. And other periods you may have no consumption. So yes, it varies in that the rate of consumption varies. It won’t go up on its own

If dosing x ml every 4 hours, and you test every 4 hours, you are adding a constant, but the consumption is variable. Then, if some tests show an alk increase, it’s because the prior 4 hour span had little or no consumption. Overall it should work out if the daily consumption is matched by an appropriate daily dose

And that's all I was saying, but aperintly this is not enough evidence for some, that ph and light is directly effect on alkalinity consumption.
If we see a trend in numbers, from a test results. Is it not good enough to put 2&2 together? Or am I missing something else?

 

[zheka757]

I do not disagree that alk consumption varies through the day, and seems to typically be highest during the light period.

We do not really know if that is because of the light itself, or because that is when pH also peaks. :)

What more proof do we need to say that lights or ph have direct effect on alk consumption, whitch is usually our corals on our tanks?