Which Alkalinity level is best for low-PH tank?

[Obriy]

My tank is almost 2 years old and I've accepted the fact that there is nothing more I can do to increase my tank PH. It's stable around 7.8.
CO2 scrubber, even with recirculation, makes not much of a difference because it's 50-gallon AIO tank and my Tunze 9004 skimmer doesn't help much. I cannot run the skimmer airline outside (new apartment building with aluminum window frames and too hot in Miami area to keep windows open).
My corals grow, very slowly, but they do.
I've recently set up automatic alkalinity control with GHL KH Director and trying to figure out which KH levels would be optimal for low PH. I've tried to ask aI and got contradicting answers. ChatGPT tells me to keep alk elevated (around 9.5) and Gemini tells me to keep it lower (around 8.0).
What do you think?

 

[Gone Reefin’]

Personally, I would let other variables and drivers determine where to keep alk. For example, you do not mention nutrients, but if they are near zero I would avoid the high end of that alk range and stay closer to 8. If you have solid nutrients, you can drift to 9.

Can you add alk in a way known to have a higher impact on pH (such as kalk)?

 

[Obriy]

I'm currently dosing 400 ml of saturated kalkwasser daily. Then, I use soda ash dosing to keep alkalinity steady with GHL dosing pumps and KH Director (12 ml daily on average).
I've tried all known ways to increase PH already and, at this point, I'm just trying to figure out whether there is an optimal alkalinity level/range for a low-PH tank.
Salinity - 0.026
Temperature - 80F
Nitrates - 10
Phosphates - 0.1
Calcium - 430
Magnesium - 1350

 

[Project1004]

I think when those who speak about doing all you can to raise the pH yet it’s not working….

I suspect something in the tank is causing it to stay low.

The problem with trying to raise the alkalinity in order to have higher pH would work if your corals can handle the higher dkh. There really isn’t much benefit to have higher dkh just to have them not use it. In order for kalk to give you higher pH is to add more and if your corals are not using them, it becomes more issue.

 

[Obriy]

The tank is located in my bedroom, which also serves as my home office. CO2 levels in the room are between 800ppm and 1300 and while I can open windows some times, I cannot keep them constantly open (Miami weather).
I'm not trying raise alkalinity to increase PH. I'm trying to find an optimal alkalinity for my current PH.

 

[Gone Reefin’]

I get where you are at and what you are asking. With those nutrient levels, anywhere from 8-9 is fine. There is no optimal level for a low pH tank unless the goal is to raise pH, which you have stated is not a goal.

 

[afboundguy]

You could try and add live plants to the room near the window that gets plenty of light to help lower CO2 levels in the room as an option...

 

[Randy Holmes-Farley Verified Community Expert]

My tank is almost 2 years old and I've accepted the fact that there is nothing more I can do to increase my tank PH. It's stable around 7.8.
CO2 scrubber, even with recirculation, makes not much of a difference because it's 50-gallon AIO tank and my Tunze 9004 skimmer doesn't help much. I cannot run the skimmer airline outside (new apartment building with aluminum window frames and too hot in Miami area to keep windows open).
My corals grow, very slowly, but they do.
I've recently set up automatic alkalinity control with GHL KH Director and trying to figure out which KH levels would be optimal for low PH. I've tried to ask aI and got contradicting answers. ChatGPT tells me to keep alk elevated (around 9.5) and Gemini tells me to keep it lower (around 8.0).
What do you think?

The higher the alk is, the higher the pH will be, all other things the same. The difference between 7 dKH and 11 dKH is about 0.2 pH units.

Both higher alk and higher pH boost the growth rate of some hard corals, but pH 7.8 is generally fine and many tanks are at that pH.

 

[Reefering1]

Both higher alk and higher pH boost the growth rate of some hard corals, but pH 7.8 is generally fine and many tanks are at

Some, or all calcifying corals?

 

[Randy Holmes-Farley Verified Community Expert]

Some, or all calcifying corals?

Some, yes. All? Don’t know since not all have been studied.

I do not recall seeing a study of a coral that did not show faster calcification at higher pH or alk. They may exist.

The question has complications as well. Are we talking about the daytime peak pH? Or the average pH? Or the night time low pH?

Are there sufficient nutrients and trace elements to support faster calcification?