pH Abnormal Readings

[dochow]

Hey all, quick question for you chemistry guys.

I have a 75 gallon mixed reef with 4 fish (2 clowns, Kole tang and Royal gramma). Lightly stocked...

25 or so gallon sump and refugium on constant light cycle.

My Salifert test consistently reads a pH of 7.6 - 7.8ish.

My APEX lab grade pH probe reads 8.26 and I even re-calibrated it yesterday with 7 and 10 pH and it was almost perfectly spot on (0.03 error).

Alkalinity is 8.6-8.9 dKH on Hanna Checker.

Using kalkwasser in ATO.

What's up??? Why the difference? Which is right???

The Salifert pH test doesn't expire for another 20months!

Thank you!!

 

[TRPlacek]

Hey all, quick question for you chemistry guys.

I have a 75 gallon mixed reef with 4 fish (2 clowns, Kole tang and Royal gramma). Lightly stocked...

25 or so gallon sump and refugium on constant light cycle.

My Salifert test consistently reads a pH of 7.6 - 7.8ish.

My APEX lab grade pH probe reads 8.26 and I even re-calibrated it yesterday with 7 and 10 pH and it was almost perfectly spot on (0.03 error).

Alkalinity is 8.6-8.9 dKH on Hanna Checker.

Using kalkwasser in ATO.

What's up??? Why the difference? Which is right???

The Salifert pH test doesn't expire for another 20months!

Thank you!!

I would go with the apex ph probe since it is calibrated.

 

[Pola0502ds]

I would borrow a friends ph test kit and compare against your test kit and you would know which is correct. In my opinion those lab grade PH probes are junk.

 

[dochow]

What pH test kits do you find are most accurate?

 

[Pola0502ds]

I use salifert too and it never matches my apex lab grade probe. Frankly, I don't test for it nor do I care. My PH is stable, it rises and falls as it should so I just leave it alone and don't even worry about it. I only pay attention to it when I need to increase my alk dosing to make sure I don't increase the PH more than .2 in a day.

 

[Brew12]

Any chance you saved one of your calibration samples so you could test it with your Salifert?

 

[dochow]

I don't think the Salifert goes down to 7 or up to 10, otherwise that would be a fantastic idea

 

[TRPlacek]

Testing with another kit is a good idea but it just seems to me that if the ph probe read spot on while calibrating then I believe the reading of 8.26 would be correct.