Practical maximum pH?

[kyleinpdx]

I've got a question that I cant seem to find a good answer to, and I know someone on here will have one! ;-)

Lets say we have a reef tank, running a high ph salt, for example red sea coral pro that at 35ppt mixes to 8.5 pH. Then say we took that reef tank and stuck it outside in the country and left it there to equalize its o2/co2 with the outside air. What is the practical maximum pH we could see? What about theoretical?

edit: changed would to could

 

[Daddy-o]

I run kalk and my reef is in the open garage. Highest was 8.6

 

[rmurken]

Take a look at this @Randy Holmes-Farley article; I think it may answer your question.

Chemistry And The Aquarium: The Relationship Between Alkalinity And pH

Randy answers many questions in this complex relationship.

reefs.com

 

[rmurken]

Also I think it’s probably easier to think of salt mixing to an alkalinity rather than a pH. The Alkalinity of the mix is the same at a given concentration (say, 35ppt), but the pH will fall within a range based on the alkalinity and CO2 situation.

That’s one reason it’s a good idea to aerate or circulate newly mixed saltwater for awhile. At first, it mixes up to a high pH because of the alkalinity. You aerate the water to introduce atmospheric CO2, which brings the pH down to something more like what’s in your tank. The alkalinity stays exactly the same from when you first mix it to when you finally put it into your tank.

Next time you mix up some saltwater, stick a pH probe in and watch it.

 

[Aero]

8.5 is the highest PH I've seen on my tanks via Apex PH probe

 

[Randy Holmes-Farley Verified Community Expert]

I've got a question that I cant seem to find a good answer to, and I know someone on here will have one! ;-)

Lets say we have a reef tank, running a high ph salt, for example red sea coral pro that at 35ppt mixes to 8.5 pH. Then say we took that reef tank and stuck it outside in the country and left it there to equalize its o2/co2 with the outside air. What is the practical maximum pH we could see? What about theoretical?

edit: changed would to could

As folks have noted, the pH of the salt mix doesn't matter.

All that matters for pH is alkalinity and the CO2 level.

While reef tanks can readily attain higher pH than the scenario in your question, if the tank is equilibrated with outside air, CO2 in the water is fixed and the pH depends entirely on the carbonate alkalinity.

At 7 dKH, the pH will be about 8.2

At 14 dKH, the pH will be about 8.5.

Of course, any tank that is deficient in CO2, due to photosynthesis or high pH additives consuming CO2, the pH can be higher. many reef tanks (including mine) ran up to about pH 8.55 with alk well below 11 dKH.

In a limewater (kalkwasser) overdose situation, the pH will temporarily spike much higher.

The graph below shows the relationship between alk and pH at different CO2 levels:

Chemistry And The Aquarium: The Relationship Between Alkalinity And pH

Randy answers many questions in this complex relationship.

reefs.com

 

[kyleinpdx]

Exactly what I was looking for. Thank you all especially @Randy Holmes-Farley always an education "talking" with you. I also tend to run between 8.4 - 8.5 (dependent on the season = how aired out the house is). I was curious, given how we know higher pH can be beneficial, why we hadn't seen folks really trying to push that parameter and I assumed there was a limiting factor/ratio/component but couldnt find the right search terms.