Daily ALK Swing ?

Chris Spaulding · Oct 29, 2022

I try to keep my ALK at about 8.2 - 8.3.
At 12:00 pm every day the ALK reads 8.2 - 8.3 but drops as the day goes on to 7.6 or somewhere in there buy about 8 pm and the rebounds to 8.2 or so by noon the next day. This is a regular pattern. Should I be worried about this swing or would you say exceptable?
Thank info Heavy SPS
Calcium Reactor effluent 28 DKH 75 mils a min
Kalkwasser 450 mils evenly throughout the day.
Dose Brightwell ALK 8.3 70 mils between 12 pm and 7 pm.

BroccoliFarmer · Oct 29, 2022

It is normal unfortunately. Drives me nuts too as the veteran say they have their all pegged perfectly whixh makes people think fluctuations are wrong. With that being said, ideally you want to minimize the swing. Trident and alkateonic can help automate your dosing to help. I have my swing band down to plus or minus .15 dkh and I’m happy with that.

Chris Spaulding · Oct 29, 2022

BroccoliFarmer said:
It is normal unfortunately. Drives me nuts too as the veteran say they have their all pegged perfectly whixh makes people think fluctuations are wrong. With that being said, ideally you want to minimize the swing. Trident and alkateonic can help automate your dosing to help. I have my swing band down to plus or minus .15 dkh and I’m happy with that.

I have the trident and the graph shows the daily swing. Was much more of a swing until I started dosing the Brightwell 8.3 when the demand started dropping

Saltyanimals · Nov 28, 2022

Interesting. We all know that we should take test at approx the same time everyday to account for the swings, but this highlights there variable in the "best time to take" a test.

Since the swings are predictable based on the graph, I assume it's best to figure out what time is the highest dkH and shoot to test at that time. What's the time pattern you're seeing with high and lows? I know pH goes with the photo period, but what about Alk?

Chris Spaulding · Nov 29, 2022

Saltyanimals said:
Interesting. We all know that we should take test at approx the same time everyday to account for the swings, but this highlights there variable in the "best time to take" a test.

Since the swings are predictable based on the graph, I assume it's best to figure out what time is the highest dkH and shoot to test at that time. What's the time pattern you're seeing with high and lows? I know pH goes with the photo period, but what about Alk?

the PH for the tank is the highest when the ALK swing is on the low side

Saltyanimals · Nov 29, 2022

And pH is the lowest in the mornings before light turns on. Which means this is when your tank Alk should also be the highest. Feels like we should be taking the alk reading right before lights on for Top-end and reading again in the evening right before lights ramp down for the Low-end.

Thanks for sharing this correlation. Will be taking readings in the mornings going forward.

Randy Holmes-Farley · Nov 29, 2022

Alk demand is highest during the day, due to both pH effects and possibly light effects directly on corals push it up, but alk can swing in other ways if dosing is anything except even 24/7.

endlessrealm · Nov 29, 2022

How do you know your trident is accurate per say? Have u tried other testers?

Saltyanimals · Nov 29, 2022

Randy Holmes-Farley said:
Alk demand is highest during the day, due to both pH effects and possibly light effects directly on corals push it up, but alk can swing in other ways if dosing is anything except even 24/7.

Thanks Randy. Which part of the day period would you say? Based on the graph above, it appears about the time pH and Alk is in reverse time correlation. I assume @Chris Spaulding 's tank like many of us and have some constant alk dosing ie. CaRX or doser heads. Assuming the readings are accurate and even if they're not precise, the graphs show that correlation if I read it right.

Randy Holmes-Farley · Nov 29, 2022

Saltyanimals said:
Thanks Randy. Which part of the day period would you say? Based on the graph above, it appears about the time pH and Alk is in reverse time correlation. I assume @Chris Spaulding 's tank like many of us and have some constant alk dosing ie. CaRX or doser heads. Assuming the readings are accurate and even if they're not precise, the graphs show that correlation if I read it right.

pH rises during the lighting period due to photosynthesis consuming CO2, and falls at night as respiration produces CO2. pH typically peaks late in the light cycle, like midafternoon. Other effects impacting this pH curve are dosing of high pH alk additives, and reverse lit refugia.

It is less clear exactly when alk demand peaks, but is typically in the mid day to mid afternoon time frame. I have curiosity about how much of that alk demand is pH driven and how much is light driven directly, and how much is abiotic precipitation (peaks with pH peaks) and how much is organism calcification (which may or may not match the pH peak).