Upper pH limit?

[Formulator]

During a recent vacation, with all the CO2 spewing humans out of our house, my pH rose significantly, topping out at 8.5 and staying above 8.2 at night. My alk consumption doubled over that time, which tells me I could benefit from permanently raising my pH. So I am now on a mission.

I’ve switched to Randy’s “bigger pH boost” 2-part recipe with NaOH which didn’t really boost my upper end, but brought my nightly bottom up from 7.8 to 8.0. I just added a CO2 scrubber today and I’m playing with the idea of incorporating kalk. Assuming all these things are additive, I don’t want to go too high with pH.

So, what is the upper limit for pH in our tanks and what is the “ideal” target? Sorry, I guess I could have just asked this up front, but I like to tell stories :rolling-on-the-floor-laughing:

 

[PharmrJohn]

Not sure of hard upper limit. But I'll be aiming for 8.2 to 8.3. Maybe 8.4. But no higher.

 

[Cali Reef Life]

Heres a good article based on it 8.3 golden zone. With 7.8 to 8.5 being safe limits.

https://www.bulkreefsupply.com/content/post/md-2020-11-how-to-raise-ph-in-your-marine-aquarium

 

[Formulator]

Not sure of hard upper limit. But I'll be aiming for 8.2 to 8.3. Maybe 8.4. But no higher.

Sounds reasonable. I get up to 8.2 briefly at the end of the bright lights period, but down to 7.8-7.9 at night. That’s with a large refugium on opposing light schedule. Ideally I would like to get my bottom at least up to 8.2.

 

[Randy Holmes-Farley Verified Community Expert]

IMO, the main problem at high pH or high alk is excessive abiotic precipitation of calcium carbonate.

Some types of macroalgae may also grow more slowly due to lower available CO2.

 

[Formulator]

IMO, the main problem at high pH or high alk is excessive abiotic precipitation of calcium carbonate.

Some types of macroalgae may also grow more slowly due to lower available CO2.

Good points. There must be a “sweet spot” though, that balance the accelerated growth with potential negatives you mentioned. Maybe 8.3-8.4?

 

[Randy Holmes-Farley Verified Community Expert]

Good points. There must be a “sweet spot” though, that balance the accelerated growth with potential negatives you mentioned. Maybe 8.3-8.4?

The sweet spot may be unattainably high, depending on what observations are being used to determine the optimal pH.

 

[ISpeakForTheSeas]

A relevant discussion that you may find interesting:
https://www.reef2reef.com/threads/high-ph-good-for-corals-bad-for-fish.1060282/