pH probe gone bad?

[Sebae]

So I've been dripping a Kalk slurry for about 36-48 hours now and have been keeping a close eye on my pH. I took out a probe I hadn't used in a while (stored in potassium chloride), calibrated it using 10 and 7 standards, and watched.

My daily pH range has been roughly 7.75 - 8.1. I just don't believe that. I am running my skimmer line outside, I keep my alkalinity around 11-12, and as mentioned am dripping a kalk slurry.

I ran a red sea color pH test this morning and came back at 8.2.

So, my question is, if the probe is calibrated at 7 and 10 standards why would it read 7.75 directly after calibration? Temperature differences are about 10 degrees F so some error there but this much?

Thanks

 

[SteveMM62Reef]

You could go to CVS and buy a Couple Bottles of Smartwater. They have a Vapor Distilled and an Alkaline Water. If I’m not mistaken, it says what the pH is on the bottle. Also see my reply about stray voltage effecting the Probes.

BTW, The Shape of the bottle makes an excellent Brine Shrimp hatching bottle.

 

[Sebae]

I'm guessing you're refering to stray voltage in the tank throwing the reading off? To test that I took a sample of water out of the tank and measured the pH. Same low reading : /

 

[arking_mark]

You can perform an indoor and outdoor cup aeration test to assess your situation.

The indoor cup aeration pH with 11.5dKH water is expected to be around 8.2 NBS with an indoor air quality of 700ppm CO2 (600 - 800 is fairly common in newer homes).

The outside cup aeration pH should be 8.4 with a normal outdoor air quality of 400ppm CO2.

 

[Malcontent]

Was it stored in a DIY KCl solution?

 

[Sebae]

It was stored in a pH probe KCL storage solution from Amazon, BIOPHARM I think was the brand

 

[Randy Holmes-Farley Verified Community Expert]

I would not use the Red Sea pH color test as an indication that the meter is not working.

Does it correctly read the pH 7 and 10 solutions after calibration?

It might be accurate, the buffers may be off, there may be electrical interference, or it may be inaccurate for other reasons.

Usually, if a probe can correctly read 7 and 10 after calibration, the probe/meter is OK.

 

[Sebae]

Thanks Randy.

If know the alkalinity of my water and the ph measured inside, the ph of the same water after 30 mins of aeration outside and assume an outdoor co2 concentration of 400 ppm, would it be possible to estimate my indoor co2 concentration?

 

[arking_mark]

Thanks Randy.

If know the alkalinity of my water and the ph measured inside, the ph of the same water after 30 mins of aeration outside and assume an outdoor co2 concentration of 400 ppm, would it be possible to estimate my indoor co2 concentration?

Given a pH and Alk you can calculate the CO2 concentration in the water. If the water was in equilibrium with the air, you can calculate the CO2 concentration in the air.

In our enclosed tanks, there is often a small difference between air equilibrium and tank CO2 levels.

Using a cup aeration test, you can bring you tank water to equilibrium with air and using alk and pH measurements calculate your CO2 concentrations.

I'm happy to run #s for you.

 

[Sebae]

So I took a cup of tank water outside with an air stone most of the afternoon, at least 3-4 hours. The ph in that sample rose to 8.2 with an alk of 10.8. This sounds wacky to me?

 

[Sebae]

Given a pH and Alk you can calculate the CO2 concentration in the water. If the water was in equilibrium with the air, you can calculate the CO2 concentration in the air.

In our enclosed tanks, there is often a small difference between air equilibrium and tank CO2 levels.

Using a cup aeration test, you can bring you tank water to equilibrium with air and using alk and pH measurements calculate your CO2 concentrations.

I'm happy to run #s for you.

Could you run… pH 8.02 and alk 13.4? Thanks

 

[arking_mark]

Could you run… pH 8.02 and alk 13.4? Thanks

 

[arking_mark]

So I took a cup of tank water outside with an air stone most of the afternoon, at least 3-4 hours. The ph in that sample rose to 8.2 with an alk of 10.8. This sounds wacky to me?

Probably very reasonable given the accuracy of our hobby kits.

 

[Randy Holmes-Farley Verified Community Expert]

So I took a cup of tank water outside with an air stone most of the afternoon, at least 3-4 hours. The ph in that sample rose to 8.2 with an alk of 10.8. This sounds wacky to me?

Wacky? Sounds reasonable to me.