Alkalinity or pH stability?

Morpheosz · Mar 29, 2023

So here's a question - I've been playing around with my CO2 scrubbing and Soda Ash dosing to see if I could stabilize my pH and avoid it getting too high during the day. Now that I have an air exchanger on the house and a scrubber on the skimmer, my pH can exceed 8.5 during the day. So I thought I'd try an experiment and dose my alk at night and that did smooth things out a bit. I was now in the 8.25-8.4 range BUT I tested my alkalinity at the end of the day today just for fun and noticed it dropped .6 dkh during the day (more than I'd expected!).

So here's the question - what would my inhabitants be happier with - a stable alkalinity but big daily swings in pH, or lower pH swings but a bigger alkalinity that fluctuates daily?

PeterC99 · Mar 29, 2023

Which inhabitants are you talking about?

Morpheosz · Mar 30, 2023

Mixed reef, lots of coral of all varieties.

Randy Holmes-Farley · Mar 30, 2023

There’s no perfect answer, IMO.

This might be worth a read;

Alkalinity stability? pH stability? Are they even different?

It is currently the dogma of the reef aquarium hobby to say that alkalinity stability is very important for SPS corals, and that pH is not. Often, the very idea of someone trying to optimize pH is called “chasing numbers” as if that statement by itself shows it to be foolish. Since I have...

www.reef2reef.com

mattb2989 · Apr 18, 2023

@Randy Holmes-Farley high mate. Im getting alk raising during the day and dropping at night. Dosing equal parts over a 24 hour period. My hanna and salifert match exactly what my kh monitor gives when the monitor gives its lowest reading over a 24hr period then the monitor raises. Could this be the monitor has the ability to detect total alk where hanna and salifert kits cant?

My lights come on at 12pm and off at 10pm. Could the raise during lighting period be down to the differences you stated with bicarbonate delta?

Randy Holmes-Farley · Apr 18, 2023

Hanna and Salifert, and any alk test that uses an acid for as titration of alk are detecting total alk.

Im not sure why you apparently see more alk consumption at night.

mattb2989 · Apr 18, 2023

@Randy Holmes-Farley no idea mate. Hanna and salifert match the kh monitor when the monitor gives its lowest reading. Then the monitor kh gives higher readings during the day as the ph rises. Im dosing 2 part with sodium hydroxide. Then as soon as the lights start dimming and off. Alk level drops again

Randy Holmes-Farley · Apr 18, 2023

mattb2989 said:
@Randy Holmes-Farley no idea mate. Hanna and salifert match the kh monitor when the monitor gives its lowest reading. Then the monitor kh gives higher readings during the day as the ph rises. Im dosing 2 part with sodium hydroxide. Then as soon as the lights start dimming and off. Alk level drops again

You sure you are not showing pH in the alk column?