When to dose Alk to avoid pH swing

[clown99]

Need enlightenment. I've been dosing Alk/Ca/Mg 1.5mL/hr, 15 min apart at every hour, starting at 2:00AM to 6:00AM.
From the graph below, on Jan 18 for instance, I noted the times of lowest and highest pH values:
2:30AM 7.94
4:15AM 7.93
6:15AM 7.95
7:45AM 7.93
5:45PM 8.23

So when would be the best times to start & end dosing, if nothing else is changed (lighting, flow, etc)? Thanks in advance.

 

[Randy Holmes-Farley Verified Community Expert]

Dosing high pH additives late at night into the early AM minimizes the pH swing, but dosing any alk additive during the day will minimize the alk changes because it is used more during the day. It's up to you and your system which is more important.

In your case, since the pH low is not that low (not below pH 7.8), stabilizing alk may be more important/useful.

 

[brmc1985]

I agree with Randy. Your PH is fine and you should really look at spreading the doses out through the day to minimize alk swings. What does your alk look like throughout the day? If you have a refugium you could look into running it opposite hours of your display. That will help a bit with the lows.

 

[clown99]

So should I measure Alk during the day to see when the low/high is occurring before adjusting the dosing time?

 

[brmc1985]

So should I measure Alk during the day to see when the low/high is occurring before adjusting the dosing time?

Do you have a trident? Otherwise I would measure through the day every couple hours to see how much it is dropping through the day and which times are the highest usage.

 

[Randy Holmes-Farley Verified Community Expert]

So should I measure Alk during the day to see when the low/high is occurring before adjusting the dosing time?

How much alk do you dose in a day (in dKH)?
If you just spread the dose out through the prime daylight hours, that goes a long way to stabilizing it.