Does alkalinity change throughout the day?

ronnie · Sep 24, 2014

As the day goes, pH increases, but does that have any effect on alkalinity?

Dosing alk causes pH to jump, so I was curious if it was a two way street.

And I'm super glad to have you here Randy! I enjoy your articles and reading the responses!

Randy Holmes-Farley · Sep 24, 2014

Thanks very much, glad to be here!

Alkalinity is on a one way trip down, except when you add some somehow. So it does not fluctuate due to natural processes like pH does.

ronnie · Sep 24, 2014

Thanks Randy! I ask because I have started testing alk on a daily basis for the next two weeks (home anyways). I wondered if there was an optimal time to test. I'm currently raising my alk from 7 to 8.5 or 9, and doing that in .5 increments. So I'm dosing 20ml twice daily. Once in the morning and once at night. I test prior to dosing.

Is the 12ish hours enough time for the alk to settle? Or should I only test after 24hrs?

Randy Holmes-Farley · Sep 24, 2014

As soon as the alk dose mixes in you can test again. That might be only 5 minutes in a sumpless tank, but might be an hour or more in an extended system with sumps and refugia.

I'd probably measure just before dosing at the same time each day (althogh hopefully you won't need to measure every day for long).

ronnie · Sep 24, 2014

Thanks again. I'm testing more just to get into the habit than anything else. I'm atrocious at it. Lazy reefer with my auto water change and top off.

Randy Holmes-Farley · Sep 24, 2014

I'm lazy too, so I understand.

Happy Reefing.

TheReefKeeper · Sep 24, 2014

Glad this was addressed I've been curious about this forever and never really ask lol finally got my answer Thanks

NanaReefer · Sep 24, 2014

Haha me too!! Ronnie I'm going through the exact same thing

Randy also addressed this for me and in such a simple manner that I'm no longer worried about crashing my tank.

chopper320 · Sep 24, 2014

To tack on to this question, does alk consumption change daily assuming no coral has been added or removed? I realize that as coral grows or more coral is added that more alk will be consumed but I'm having a really hard time dialing in my 2 part dosing.

I'm testing every other day and trying to adjust the amount of dosing to keep it stable but with minor tweaks sometimes it drops or rises pretty drastically. For example it may drop from 9.3 to 8.3 in two days. Then I increase my dosing by .6 ml/day and 2 days later my alk is at 9.6 again. It just seems wildly inconsistent.

ritter6788 · Sep 24, 2014

chopper320 said:
To tack on to this question, does alk consumption change daily assuming no coral has been added or removed? I realize that as coral grows or more coral is added that more alk will be consumed but I'm having a really hard time dialing in my 2 part dosing.

I'm testing every other day and trying to adjust the amount of dosing to keep it stable but with minor tweaks sometimes it drops or rises pretty drastically. For example it may drop from 9.3 to 8.3 in two days. Then I increase my dosing by .6 ml/day and 2 days later my alk is at 9.6 again. It just seems wildly inconsistent.

If you're not dosing anything else then I'd look at testing error. Also don't be afraid to test everyday or multiple times a day before and after dosing to figure out exactly what you are putting in and your usage.

How are you dosing?

chopper320 · Sep 25, 2014

I have 1.1ml/min dosers setup u on an apex. I dose around 30 secs each hour and adjust from there. Right now I'm at 26 secs per hour.

I've tested with multiple delivery kits and get the same results. This has been an ongoing issue for me for about a year. I have a healthy sps tank but I just can't get a stable alk. I guess the other possibility if it's not change in consumption is that my doser is faulty and not staying consistent.

Velodog2 · Sep 25, 2014

I would add that you need to keep in mind the accuracy of the test kit and not draw conclusions based on "small" fluctuations seen as a result of the natural error.

Randy Holmes-Farley · Sep 25, 2014

While calcification may change day to day if other things change (lighting/pH, etc.), most people find that true steady dosing results in fairly steady alkalinity.

I suspect the effect you are seeing is either changed dosing, or kit variability. Kits vary a lot more than many people like to think.

ronnie · Sep 25, 2014

Dosed 25ml last night, and have brought my alkalinity up to 8.4 as expected. I'm going to do one more day of two doses @25ml to raise it to around 9, and then start a maintenance dose of 23ml per day to maintain