Alk, ph, and time of day.

[ctripi]

Is pH and Alk interconnect so much as to be influence by what time of day we test our systems parameters (considering the normal pH variance through a 24 hour period)?

Thanks in advance.

[HighlandReefer]

Low pH: Causes and Cures
http://www.reefkeeping.com/issues/2004-09/rhf/index.php

From Randy's article:

http://www.reefkeeping.com/issues/2004-09/rhf/images/Figure1.jpg

Figure 1. The relationship between alkalinity and pH for seawater equilibrated with air containing normal and elevated carbon dioxide levels. The green dot shows natural seawater equilibrated with normal air, and the curves reflect the result that would be obtained if the alkalinity were artificially raised or lowered.

So, if your alkalinity drops enough from consumption during the day and you only supplement infrequently, this can have an effect on your pH. Also as the CO2 concentration in your tank increases during the day pH will increase and the opposite occurs at night which results in a pH drop.

[ctripi]

Thanks for the reply but I'm not sure if I asked the question correctly.

Should I consistently test ALK the same time each time to avoid variability pH may contribute to the result?

(FWIW I run a two-stage calcium reactor and ofset pH with saturated kalk.)

BTW entomology is cool career.

[HighlandReefer]

It should not matter what time you test alkalinity. Testing your pH should be the same time every day.

Yes, I find Entomology rewarding, but after 35 years I have found the ocean very interesting too and a nice change. :)

[bertoni]

pH doesn't affect alkalinity, so that's not an issue. Tank alkalinity can vary quite a bit throughout the day if it's being dosed in one shot. A daily drop of 2-3 dKH is not uncommon.