Red Sea PH Test Vs Freshly Calibrated Neptune PH Probe

[Raxnar]

Looking for some opinions.

Tonight we re-calibrated our Neptune Probe using PinPoint PH 7 and 10 solutions.
Both temperature acclimated to 25C.

After Calibration the Neptune Probe is reading a PH of 7.74.

Using the Red Sea PH test that came with the Maturation kit, a chemical test, it reads ~8.1-8.2.

Which is likely to be more reliable?

Before we re-calibrated the Neptune Probe it was reading 8.8.

 

[Randy Holmes-Farley]

I cannot say which (if either) is accurate.

Generally, pH meters are more accurate than kits, which, unfortunately, are not easily calibrated or checked. I also think many pH kits are likely unsuitable for seawater (regardless of the claims), although the Red Sea may be OK.

When you calibrated the Neptune, did you go back and verify that it correctly read the pH calibration fluids?

For reasons I do not understand, an unusually high number of folks have problems with pH and conductivity measurements from aqaurium controllers, perhaps in part due to temperature issues.

If you live in a suitable climate, try this aeration test. If the pH is really that low and you aerate with outside air, the pH will rise. If it is 8.1-8.2, it won't.

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.

 

[Cory]

I agree with Randy and think the aereation test is a good idea.

If you have a forced air furnace and its cold where you are id say the test kit is right.

 

[Raxnar]

I don't have time until after work to do a proper control test.

I did omit some key data. 2 days ago I attempted the Soda Water lowering tactic. The reason is the Neptune Probe was reading 8.8-8.9 for a few days.

So if it really was out of calibration I was fighting a battle I didn't need to.

Over night with aeration ( I currently run aeration off cycle to my lights 23:30 to 09:30).

Over night last, PH has risen slightly from 7.74 to 7.77. I'll crack the den window now as I have to get to work, lets see if that helps it over the next ~8 hours.

If i hadn't done the Soda water adjustment I'd be sitting right around 8-8.1.

 

[Raxnar]

Checkpoint.

Up to 7.82 since I posted earlier today.

If this trend continues, it would seem that there is excess CO2 in our house, enough to affect the water PH.

 

[Raxnar]

I agree with Randy and think the aereation test is a good idea.

If you have a forced air furnace and its cold where you are id say the test kit is right.

We do indeed have Forced air heating/cooling. Outside Temp is currently ~6C and we maintain the inside temperature at a comfortable 20C.

With the windows open it is showing a steady rise in PH now that the window is open just after ~4 hours.

With aeration over night, ~8 hours, and inside air, it only rose .03 PH. in the ~4 hours today with outside air being introduced it rose .05 PH. Nearly double the 8 hour increase. Make that .06, the reading changed as I was writing so it is double the overnight change now.

I may have to drill a hole in the wall to feed the air pump, thankfully that will be easy.

 

[Raxnar]

Still trending upwards.

The reading is now 7.91 PH.

 

[Raxnar]

Was up to 7.95 when I got home tonight.

I decided to re-do the calibration, for S**Ts and giggles.

Steps:
1) place Calibration solution in SUMP to bring up to temperature.

2) Wait 60 minutes.

3) Soak in Cleaning Vinegar and RODI Water for a 60 seconds. (this is double strength vinegar meant for cleaning)

4) Rinse in RODI Water for 60 seconds.

5) Open 7 PH Calibration Fluid

5a) Insert PH Probe and Digital Thermometer.
5b) Wait for temperature to normalize.

6) Begin Manual calibration.

6a) 7 PH calibration stabilized for 30 seconds at a reading of 730.

7) Finish 7 PH Calibration.
7a) Set aside Calibration fluid in a way to keep it warm in the sump for future test.

8) Rinse PH Probe in RODI water.

9) Open 10 PH Calibration Fluid.

9a) Insert PH Probe and Digital Thermometer.
9b) Wait for temperature to normalize.

10) Begin 10 PH Calibration process.
10a) 10 PH Calibration stabilized for 30 seconds at a reading of 1026.

11) Finish 10 PH Calibration.

12) push/upload to apex.

13) Rinse Probe in RODI Water.

14) Get Reading in RODI Water of 2.7 PH.

15) Test 7 PH with probe back in calibration solution.
15a) Results in a 7.0 reading.

16) Rinse Probe in RODI Water.

17) Get Reading in RODI Water of 2.7 PH.

18) Test 10 PH with probe back in calibration solution.
18a) Results in a 10 reading.

19) Place PH Probe back in rack in sump.

20) PH Reading of 7.92

*note, sorry about the double spacing, helped me write it and read it

Test sump water with Red Sea Test kit that came with the maturation kit, get a reading of 8.2-8.3... same as yesterday.

If the calibration gave such exact results against the calibration solution I'm leaning to trusting the probe over the test kit I have.

Can Test kits expire resulting in a "off" reading? I would like to find a reliable backup PH checker, not convinced this individual Red Sea batch of PH Checker is ok. They have a "Pro" kit which is more $ but is it more reliable? no idea.

I'll see if the PH comes back up tomorrow with the window open again but it seemed to stop at 7.95 today.

Anyone have experience with the Hanna HI98108 testing pen?

By the way, @Randy Holmes-Farley and @Cory Thank you for chiming in with the assistance.

 

[Raxnar]

PH was back to 7.95 by the time I hit the sack last night but dropped over night to 7.81.

Window cracked again for today to see if it helps. Just turned on the air stone ~10:20am.

 

[Raxnar]

Back up to 7.91 so far today.

Seems I need a fresh air vent in the room. Should also check our HVAC system as it should be drawing in fresh air somewhere. Or perhaps it is and this room in particular just needs a bit more fresh air.

 

[Raxnar]

And were back to 7.95 PH based off the Neptune Probe. the Red Sea kit still says 8.2-8.3.

Tomorrow I'll leave the Den window closed, but I'll also check Alkalinity tonight to make sure were not low.

If Alkalinity is ok, would it be best to consider limewater dosing?