When should you care about pH?

[FunkEngine]

I recalibrated the probe tonight. It increased the reading by about .15 to .2. Which is good, because I saw it reporting 7.38(!) the other night as a low. Which isn't to say it's where it should be. I'll be trying to aerate a sample tomorrow to try to confirm a CO2 issue.

 

[FunkEngine]

Update: Aerated some water outside with an airstone for 10 minutes, wrapped in saran wrap and warmed back up, it went from 7.64 to 7.96. Is this where "low" CO2 water should be testing? I want to make sure my probe is still reasonably accurate.

 

[Brew12]

Update: Aerated some water outside with an airstone for 10 minutes, wrapped in saran wrap and warmed back up, it went from 7.64 to 7.96. Is this where "low" CO2 water should be testing? I want to make sure my probe is still reasonably accurate.

I would have expected you to be in the 8.2 to 8.3 range. I think your probe still isn't reading correctly. The other possibility is that your alkalinity is much lower than you think it is.

 

[FunkEngine]

I would have expected you to be in the 8.2 to 8.3 range. I think your probe still isn't reading correctly. The other possibility is that your alkalinity is much lower than you think it is.

It passed calibration, and unless these are a bad batch, it should be fairly close. I'll do another aeration test but set it out longer, maybe 20-30 minutes to see if that will make a difference.

I use the Hanna checker for alkalinity with eppendorf pipettes for consistency and accuracy, so test technique is about as spot on as it gets. Baring bad reagent or meter these numbers should be spot on within the tolerances of the meter. I'll see if I can have the LFS verify my alk numbers.

 

[Brew12]

It passed calibration, and unless these are a bad batch, it should be fairly close. I'll do another aeration test but set it out longer, maybe 20-30 minutes to see if that will make a difference.

I use the Hanna checker for alkalinity with eppendorf pipettes for consistency and accuracy, so test technique is about as spot on as it gets. Baring bad reagent or meter these numbers should be spot on within the tolerances of the meter. I'll see if I can have the LFS verify my alk numbers.

After you do the calibration have you put the probe back into a calibration fluid to see what it reads?

I know I'm grasping at straws but I don't understand why you are seeing what you are. I can't help but think it is a bad probe.

 

[FunkEngine]

Did another aeration test, this time 35 minutes outside with the airstone. Its reading 7.94, which I'm willing to call the same as the previous test.

After you do the calibration have you put the probe back into a calibration fluid to see what it reads?

I know I'm grasping at straws but I don't understand why you are seeing what you are. I can't help but think it is a bad probe.

I did not. I have a couple more calibration packets on hand I can see what they read.

 

[Randy Holmes-Farley Verified Community Expert]

I generally wouldn’t try to use the aeration test to evaluate calibration exactly. The pH went up a lot with outdoor aeration, and that clearly says the pH is quite low.

 

[FunkEngine]

I generally wouldn’t try to use the aeration test to evaluate calibration exactly. The pH went up a lot with outdoor aeration, and that clearly says the pH is quite low.

That's fair haha. So, given the numbers I'm reading, is pH worth worrying about here? And if so, would a CO2 scrubber be an adequate solution? I'd somewhat prefer a refugium, but my size is severely limited and my nutrients are already near trace, so I'm not sure if it would be a good fit here.

 

[Randy Holmes-Farley Verified Community Expert]

If you like to find things to tweak, pH seems like a good opportunity. If hard corals seem to thrive, and you aren’t into tweaking, I wouldn’t worry to much. [emoji3]

 

[Brew12]

I generally wouldn’t try to use the aeration test to evaluate calibration exactly. The pH went up a lot with outdoor aeration, and that clearly says the pH is quite low.

Didn't one of your articles have a chart showing what pH should be based on typical outdoor CO2 readings for a given alkalinity? I was looking but couldn't find it.

 

[Gareth elliott]

What is your salinity at? At the alkalinity levels that a reef is kept at high salinity can decrease the ph on measurable level. Can happen if salt creep fell back into the tank in appreciable amounts.

 

[Randy Holmes-Farley Verified Community Expert]

I do show graphs of pH vs alkalinity in some of my articles, but we aren’t sure what his outside CO2 level actually is, and I speculate that aeration at low temps drives in more gas (it would for O2, N2, but CO2 is more complicated), giving a lower pH even after warming up.

 

[Randy Holmes-Farley Verified Community Expert]

What is your salinity at? At the alkalinity levels that a reef is kept at high salinity can decrease the ph on measurable level. Can happen if salt creep fell back into the tank in appreciable amounts.

Why do you think that? I don’t think higher salinity reduces pH for a given alkalinity and CO2 level.

 

[Gareth elliott]

Why do you think that? I don’t think higher salinity reduces pH for a given alkalinity and CO2 level.

NaCl is a salt of a strong base and a strong acid. When dissolved With no other ions acting on its its ph is 7. When added in large enough quantities to a body of water it pushes the ph towards neutral. In an acidic solution ph rises in an alkaline solution it lowers the ph. I could be quite wrong on my understanding of this reaction but only caused a minute of checking refractometer

 

[Randy Holmes-Farley Verified Community Expert]

NaCl is a salt of a strong base and a strong acid. When dissolved With no other ions acting on its its ph is 7. When added in large enough quantities to a body of water it pushes the ph towards neutral. In an acidic solution ph rises in an alkaline solution it lowers the ph. I could be quite wrong on my understanding of this reaction but only caused a minute of checking refractometer

The fact that sodium and chloride are neutral means it has no direct effect on pH, whatever the pH is, not that it pushed the pH toward 7. If I have sodium hydroxide solution at pH 10, I can add nearly any amount of sodium chloride to it and that does not move the pH toward 7. [emoji3]

 

[Gareth elliott]

The fact that sodium and chloride are neutral means it has no direct effect on pH, whatever the pH is, not that it pushed the pH toward 7. If I have sodium hydroxide solution at pH 10, I can add nearly any amount of sodium chloride to it and that does not move the pH toward 7. [emoji3]

Thank you

 

[Randy Holmes-Farley Verified Community Expert]

You’re welcome.
Happy reefing. [emoji3]