Low ORP & Low Ph

[Scungili]

I just received my pinpoint ORP meter. Calibrated it to 400 and tried it out.
So far ORP is reading 183Mv This I understand will adjust with time?

This is more concerning:

I received my Ph adjustment packets at 7.00. I was surprised to see that my meter was reading .38 too high. I opened another $3 calibration packet just to make sure and it was the same.

I adjusted to find a Ph reading of 7.83 in my tank after the MH lights were on for 7 hrs.

I have Cyano growing on sand and a GHA growing as on rocks and glass.

NO3 is undetectable with Lamotte
PO4 is 0.0 on Hanna

Ca 500 Mg 1450 Alk 130ppm

Any thoughts?

 

[Scungili]

I also failed to add I was dosing Carbon (Vodka) and about 2 lbs of Biopellets in 2 reactors. I was ignorantly trying to get rid of my GHA and Cyano only to find it slowly growing more and more. I have stopped as of 1 week ago.

10 min later my ORP is 188.

 

[Scungili]

Orp is now 235 so it definitely needs to adjust. My only concerns are the ph which I started dosing more soda ash mix to up it. Would low Ph cause GHA and Cyano or no?

 

[Randy Holmes-Farley]

Uncalibrated pH meters can be way off with no problems at all. You also need to use two pH values to calibrate. Did you use something else like pH 10?

This has more:

Measuring pH with a Meter
http://www.advancedaquarist.com/issues/feb2004/chem.htm

and

A Comparison of pH Calibration Buffers
http://reefkeeping.com/issues/2005-02/rhf/index.htm


ORP can take at least 24 h to equilibrate. This has more:

ORP and the Reef Aquarium
http://reefkeeping.com/issues/2003-12/rhf/feature/index.htm

 

[Scungili]

no i just ordered some thanks randy

 

[Randy Holmes-Farley]

You're welcome.

Good luck.

 

[Scungili]

Randy since I only calibrated with 7.0 would I at least be closer to the actual Ph than no calibration at all given that I haven't calibrated this monitor ever in the year I've had it? I know, now I realize how dumb that is...

I think it will be a week before I get the 10.0.

 

[bertoni]

Maybe. You could try checking basic accuracy using borax:

http://classic-web.archive.org/web/...twork.com/fish2/aqfm/2000/feb/bio/default.asp

 

[Scungili]

Ok that's a good temporary solution till I get the Milwaukee packets in.

My ORP was at 260 in the evening after several hours of light. In the morning it's about 300. Does this make sense?

 

[Randy Holmes-Farley]

Yes, those ORP values are reasonable and not unusual.

 

[Scungili]

So my main concern is Low pH and Low Alk at 110ppm.

I've been dosing with Soda Ash solution slowly. pH is now 7.85 +/-

Would I at least have calibrated closer to accurate with the 7.0 only?

10 pH is coming in the mail.

 

[Randy Holmes-Farley]

I would not do anything about pH now. Just boost the alk as necessary.

 

[MattAndKim]

You don't necessarily have a more accurate measurement from determining the bias alone with the 7 buffer. Whether or not it was more accurate depends on the slope of the probe, which can only be determined with a multi-point calibration. It's probably more accurate. Did you check the measured pH against the temperature dependent expected buffer pH?

 

[Boomer]

Scungili

Your pH meter just calibrated a 7 should be fine for now, as there are pH meters that only have one-point calibration. Who's pH meter do you have ?

 

[MattAndKim]

If your meter only accepts a one-point calibration, that just means it cannot interpolate pH properly with a probe that does not still respond with 100% of ideal generated electric potential. pH probe slopes continually degrade even when cared for by professional chemists, in your fish tank they will go bad even faster. You should not put too much weight on a pH reading given by an inexpensive meter with a single-point calibration.

 

[bertoni]

I agree that the pH at 7.8 is fine, and I wouldn't do anything drastic at this point.