If you pH is less than 7.8, your pH meter is probably wrong

[Randy Holmes-Farley Verified Community Expert]

I still get a pH of 7.8 NBS with 7 Alk and 1250 ppm CO2 level. Again assuming a well aerated tank.

OK, so a little higher in CO2 will drop it lower, and a CO2 level not in equilibrium can be lower still.

A better title might be:

"If you pH is less than 7.8, one important thing to check is pH calibration"."

 

[Bleigh]

A friend just changed out his sump on his tank. His original had multiple baffles. His new one has only one. His PH is now 7.8 where in the past it was 8.3

Agreed with @Randy Holmes-Farley. You can have plenty of O2 and still have lower ph. Ph is related to how CO2 reacts in water when dissolved.

 

[Bleigh]

OK, so a little higher in CO2 will drop it lower, and a CO2 level not in equilibrium can be lower still.

A better title might be:

"If you pH is less than 7.8, one important thing to check is pH calibration"."

Much clearer title suggestion.

@arking_mark as you probably noticed, few people will follow a link. Lol. Best to give too much info when making posts. It can sometimes feel condescending when I do that, but I think people appreciate more info overall.

 

[piranhaman00]

I use a very nice ph meter and I have had below 7.6 with many people in house

 

[arking_mark]

OK, so a little higher in CO2 will drop it lower, and a CO2 level not in equilibrium can be lower still.

A better title might be:

"If you pH is less than 7.8, one important thing to check is pH calibration"."

I honestly believe that many of our hobby-grade calibrated pH meters are inaccurate and don't give reasonable measurements. This leads to tons of reefers spending time and money correcting non-problems.

 

[Randy Holmes-Farley Verified Community Expert]

I honestly believe that many of our hobby-grade calibrated pH meters are inaccurate and don't give reasonable measurements. This leads to tons of reefers spending time and money correcting non-problems.

I agree with that.

 

[arking_mark]

I use a very nice ph meter and I have had below 7.6 with many people in house

Let's investigate this claim.

I'll assume your tank is well aerated, not super overstocked, and you're not dosing anything that lowers pH.

I'll also assume a 7.5 dKH.

To achieve that 7.6 NBS pH, the house CO2 level would have to be at roughly 2200 ppm. At this level, you are beyond stuffy and entering dizziness, nausea, cognitive impairment, and possible dysfunction with extended exposure.

Were you really at a pH of 7.6? Was the house air beyond stuffy? Or maybe that measurement was inaccurate?

 

[piranhaman00]

Let's investigate this claim.

I'll assume your tank is well aerated, not super overstocked, and you're not dosing anything that lowers pH.

I'll also assume a 7.5 dKH.

To achieve that 7.6 NBS pH, the house CO2 level would have to be at roughly 2200 ppm. At this level, you are beyond stuffy and entering dizziness, nausea, cognitive impairment, and possible dysfunction with extended exposure.

Were you really at a pH of 7.6? Was the house air beyond stuffy? Or maybe that measurement was inaccurate?

It’s not well aerated , no skimmer and lids ,

Also your chart and math are beyond BS, no idea what you are talking about

I would love to see how you come to that conclusion

 

[Mywifeisgunnakillme]

I think it's a great title for the thread--it's just provocative--and look at all the great in depth responses it spurred so that everyone can be better informed.... A more boring title would not have generated such a nice discussion.

 

[slythy]

It’s not well aerated , no skimmer and lids ,

Also your chart and math are beyond BS, no idea what you are talking about

I would love to see how you come to that conclusion

In planted tanks you can easily gas out (kill a fish) at like 60ppm… I think in a home aquarium 400 would be instant death.

that charts for air not water. Look at kh/ph/co2 charts thats a decent estimate on ppm

Also it doesnt take much ripple at the surface for decent 02 exchange.

 

[arking_mark]

It’s not well aerated , no skimmer and lids ,

Also your chart and math are beyond BS, no idea what you are talking about

I would love to see how you come to that conclusion

Well if your tank isn't well aerated, then 7.6 pH can be achieved.

No BS, there is a defined relationship between Alk/pH/CO2 with a corresponding mathematical model and python library that allows me to punch in numbers to get results.

The chart was pulled off Google and their are many studies on the effects of higher CO2 levels.

 

[hart24601]

I think this is the issue:

I'll assume your tank is well aerated, not super overstocked, and you're not dosing anything that lowers pH.

I don’t think it’s wise to make that assumption as many tanks are not aerated to the point of equilibrium and carbon dosing or calcium reactor can easily lower pH of course that is tied to the well aerated item. Many systems now don’t even run skimmers or run them part time.

 

[slythy]

Well if your tank isn't well aerated, then 7.6 pH can be achieved.

No BS, there is a defined relationship between Alk/pH/CO2 with a corresponding mathematical model and python library that allows me to punch in numbers to get results.

The chart was pulled off Google and their are many studies on the effects of higher CO2 levels.

I think that chart is for air quality. Co2 levels in water in the 400ppm i think would be massively high and would gas out the fish. Ive seen fish gassed out at like 60ppm.

 

[arking_mark]

I think this is the issue:

I'll assume your tank is well aerated, not super overstocked, and you're not dosing anything that lowers pH.

I don’t think it’s wise to make that assumption as many tanks are not aerated to the point of equilibrium and carbon dosing or calcium reactor can easily lower pH of course that is tied to the well aerated item. Many systems now don’t even run skimmers or run them part time.

Those caveats were made in the post.

 

[hart24601]

Those caveats were made in the post.

Of course however it’s irrelevant to the original claim. It’s quite common.

Randy’s adjustment of the title to:

"If you pH is less than 7.8, one important thing to check is pH calibration".

Seems quite wise as a statement like the title that then needs to have assumptions then added isn’t the best particularly if those assumptions are not standard conditions for many tanks.

 

[hart24601]

Although the idea of the original statement with an * behind it which says in fine print at the bottom the various assumptions does make me laugh.

Acros are easy!*

*assuming stable water conditions for 6 months at least along with adequate lighting and water flow and compatible livestock

 

[arking_mark]

All points are well taken.

Generally speaking, I still contend that most readings below 7.8 will be due to testing inaccuracy and error. Most modern tank setups have adequate flow for aeration and most using advanced equipment such as a CaCO3 reactor know what they are getting into.

 

[alton]

Lol. pH is not a measure of Oxygen.

I'm not sure how that is a response to the fact that pH and O2 are not directly related.

CO2 is the gas that controls pH.

CO2 is sometimes is related to O2 (say, by photosynthesis or respiration) and sometimes not (say, by alk additives consuming CO2, or CaCO3/CO3 reactor adding CO2, etc.).

Changing any mechanical aquarium aspect that alters aeration may impact O2, but the effect on pH is by altering CO2 exchange. Your friend is probably driving high CO2 air into the water with those baffles.

He went from multiple baffles to just one. I had this issue in the the early 90's when I had my 135 filtered with a wet dry and bio bale but then I set up a 29 gallon with an undergravel filter with air stones. After complaints from my wife with salt creep on her wall I placed a power head on top of one of the tubes which provided plenty of flow but my PH went way down so I had to buffer everyday. I finally took the tank down. If you have a tank that is well Oxygenated, you won't have an issue with CO2. So many have a tank with a sump and return that does not have produce enough oxygen in the water.

 

[Randy Holmes-Farley Verified Community Expert]

He went from multiple baffles to just one. I had this issue in the the early 90's when I had my 135 filtered with a wet dry and bio bale but then I set up a 29 gallon with an undergravel filter with air stones. After complaints from my wife with salt creep on her wall I placed a power head on top of one of the tubes which provided plenty of flow but my PH went way down so I had to buffer everyday. I finally took the tank down. If you have a tank that is well Oxygenated, you won't have an issue with CO2. So many have a tank with a sump and return that does not have produce enough oxygen in the water.

The baffles experiment says nothing about what caused the pH change.

CO2 (and pH) DO NOT move in lockstep with O2 in a reef tank. They can move in the same direction or in opposite directions, depending on what processes are taking place. High oxygenation definitely DOES NOT ensure no issues with CO2.

ALL of the following happen in reef tanks:

1. High CO2 (low pH) and high O2 (reef tanks in high ambient CO2 during the day)
2. High CO2 (low pH) and low O2 (many reef tanks at night)
3. Low CO2 (high pH) and high O2 (many reef tanks during the day)
4. Low CO2 (high pH) and high O2 (my reef tank in the afternoon: high O2 from photosynthesis and low CO2 from limewater)

 

[zdstrong]

I don’t know if this blanket statement is accurate. But it was for me. My ph was calibrated about a year ago when tank set up. By the time I realized ph is important Ph was 7.7-7.8. Went through trouble of running air line to outdoors… still low 7.8-7.9. Thought to recalibrate probe. Now reads 8.2-8.3.

I would definitely say that one should verify probe is calibrated correctly prior to trying to adjust anything