pH probe question

[Christos Ioannou]

Hi UKAPS-ers

I am using this probe and noticed the following abnormality
When probe is submerged as in A, I get funny readings (acid bath readings)
When probe is submerged as in B, I get reasonable readings.

Seems that probe cannot be submerged further than B - but not evident in the mini manual
When using a drop checker, I have been reading that one needs to place the drop checker close to substrate to understand how much CO2 is available for carpeting plants (high on my wishlist )

The above constraint makes it impossible to submerge the probe that deep in the water (tank is 35cm tall).
Should I expect that the readings at about 10cm from surface are much different from those at substrate level?
I am using a spraybar at the long side of the tank, which I believe achieves good circulation.

Thanks

 

[Chris Jackson]

hi, certainly all the probes i've had over the years have instructed me not to submerge them down to the B zone and I dont.

As long as you have good water circulation across the bottom of the tank and past the probe I think your readings should be close enough and that carpet plants will grow fine. Flow across the carpet is the key.

 

[Marcel G]

Each lab grade glass electrode should have a small filling opening in the upper end of the electrode covered by some rubber. This opening is used for refilling the electrolyte once it drops too much. When you measure the pH with the electrode, this opening should be left open so that the ambient air can get into it. This should speed up the electrode response. If you close the opening by the rubber or dip it underwater the readings could be screwed.

 

[Christos Ioannou]

Thank you both for your responses.
One more thing: is it wise to "run" the electrode and wait for a minute or two before a correct reading can be taken? Or can I take an immediate reading once I power up the electrode?

 

[Marcel G]

It's always better to wait for the reading to "stabilize" (it can take a couple of seconds, but typically rather couple of minutes).

 

[Christos Ioannou]

That's great to know. Thanks