Puzzling Alk Test Readings

[Charlie the Reefer]

Hey everyone,

I'm noticing something interesting with my alk consumption. I'm auto testing using the Neptune Trident, dosing only Kalk. Hasn't done me any wrong on Alk as far as I know. Testing 4x a day on default schedule, i.e. every 6 hours. Running 8AM - 8PM light schedule with 125G mixed reef, lots of acros/SPS.

At first I thought it was interesting how alk "consumption" was a lot higher during some intervals. I would dose a constant amount throughout the day more or less, but noticed alk would spike up and down. I.e., at 6PM it would be 8.4 then 6 hours later it would be 8.1 (indicating over consumption at that interval).

So I started tinkering with my alk dosing schedule for fun to try to flatline things out a bit (so the alk swing in those 6 hour intervals was a lot less). Came up with the below schedule... Definitely has minimized the ups and downs.

But the really curious thing is, I stopped all of the dosing between 12AM - 6AM.... But every time this is where I notice the biggest alk spike! Literally, the biggest spike in alk, according to tests, is when I'm not dosing anything at all. I noticed this before, and gradually toned the doseage down until where it's at now, 0. For the graph below of the tests from the last week, I have not dosed anything between 12AM-6AM.

So my question is... Is this most likely just some kind of weird nuance/test issue with the Trident? Or is there some kind of biological mechanism "dumping alk" into the tank from 12AM - 6AM.


Alk readings:

Kalk dosing schedule:

This issue isn't causing any issues perse, I'm just really curious to understand what's going on.

Thanks for your thoughts.

 

[Randy Holmes-Farley]

Most people find the majority of alk consumption happens during the day when the bulk water pH is highest. I am still not certain if that is a bulk pH only effect, or wholly or partly an event taking place inside corals due to light driven photosynthesis raising the internal pH and accelerating calcification.

So why do you see an alk rise at night?

The changes you show in the graph are quite small and may just be testing issues (such as the starting pH impacting the measured alk since it is a pH titration).

Or it may be from factors that really do impact alk but normally are lost under the much larger effects of calcification. For example, consumption of nitrate will add alk. If there is no calcification taking place and nitrate is being consumed at night, then you might detect a small alk rise.

You are not dosing nitrate, are you?

 

[Lavey29]

I only interval dose alk during the day when lights are on not overnight. I dose calcium overnight because I believe that is when skeletal growth occurs.

 

[Charlie the Reefer]

Most people find the majority of alk consumption happens during the day when the bulk water pH is highest. I am still not certain if that is a bulk pH only effect, or wholly or partly an event taking place inside corals due to light driven photosynthesis raising the internal pH and accelerating calcification.

So why do you see an alk rise at night?

The changes you show in the graph are quite small and may just be testing issues (such as the starting pH impacting the measured alk since it is a pH titration).

Or it may be from factors that really do impact alk but normally are lost under the much larger effects of calcification. For example, consumption of nitrate will add alk. If there is no calcification taking place and nitrate is being consumed at night, then you might detect a small alk rise.

You are not dosing nitrate, are you?

Not dosing Nitrate. Actually, the pH titration theory would make a bunch of sense, because the "low alk test" occurs when pH is ~8.45 and dropping, and it is 8.6+ for all the other tests... Didn't think about that.