Daily Alk swing

[gbroadbridge]

Recently I purchased and installed an automated Alk tester, to replace my manual daily test.

My daily test was conducted with a 0.1N HCl solution from Hanna, together with a Milwaukee MH102 pH meter with a stated accuracy of 0.02 pH. The titration was with 100ml of tank water using a 1ml syringe for the acid and usually used about 2.5 ml of acid to reach a pH of 4.5.

The auto testing gadget does the same however it uses the same acid diluted to 0.02N with a 50ml sample of tank water.

As it does the titration slowly and automagically I assume it will be more accurate.

I've attached a graph showing the daily Alk swing over one month as I find it interesting.

I have the doser automatically tweak the dosage if things go out of bounds but this is the best stability I could achieve.

I believe this shows the necessity of testing at the same time every day.

I have the control set at 7.75dkH

 

[KrisReef]

Interesting. I wonder what reefers will say about your graph, is this stability or is it not?

Thanks for posting this. Hopefully folks will join in and discuss the graph!

 

[Gtinnel]

Wow keeping alk within less than a .3 degree range is pretty impressive. I try to keep mine within a .5 window and I will occasionally be outside of it.

 

[gbroadbridge]

These are the rules (actions) that I've enabled inn order to achieve these results.

 

[thatmanMIKEson]

What equipment are you using for this?

 

[gbroadbridge]

What equipment are you using for this?

Reef Factory kH keeper and Reef factory dosing pump

They're quite new but are quite impressive compared with Neptune and GHL. (Both of which I have used previously)

Reef Factory

www.reeffactory.com

 

[Randy Holmes-Farley]

It is certainly true that alk demand is not steady 24/7, and interpretation of testing needs to take into account the variables of unsteady demand and unsteady dosing.

I do, however, worry about folks talking too much about alk swing as if it is a thing like the pH swing. In almost all cases, alk swing is a man made phenomenon caused by dosing thst is not matching demand. In the absence of dosing, alk is usually a steady decline, not a swing.

 

[gbroadbridge]

It is certainly true that alk demand is not steady 24/7, and interpretation of testing needs to take into account the variables of unsteady demand and unsteady dosing.

I do, however, worry about folks talking too much about alk swing as if it is a thing like the pH swing. In almost all cases, alk swing is a man made phenomenon caused by dosing thst is not matching demand. In the absence of dosing, alk is usually a steady decline, not a swing.

I'm quite certain that you are correct.

Alkalinity in the oceans is pretty static simply because the volume of water means that the demand is quite insigifaant

It is important to consider that a little glass box where we attempt to aproximate the ocean may not have the same dynamics as an ocean.

In this case Alkalinity and Salinity are very variable, and both affect each other .

Seeking stability is in my opinion quite important - quite up there with measurement of pH which is negrlected.

Controlling ALk and pH is quite iimportant, and that is why I posted my results.

 

[Randy Holmes-Farley]

I'm quite certain that you are correct.

Alkalinity in the oceans is pretty static simply because the volume of water means that the demand is quite insigifaant

It is important to consider that a little glass box where we attempt to aproximate the ocean may not have the same dynamics as an ocean.

In this case Alkalinity and Salinity are very variable, and both affect each other .

Seeking stability is in my opinion quite important - quite up there with measurement of pH which is negrlected.

Controlling ALk and pH is quite iimportant, and that is why I posted my results.

Ok, I agree that if salinity is not constant, alk can rise and fall a small amount with it, but otherwise, there’s not any significant mechanism other than dosing for the rise part of an alk swing.

The only caveat is in a tank with almost no alk demand, where slow dissolution of rock and sand can lead to alk additions dominating over demand.