PH accuracy?

kilnakorr

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I got a new PH monitor today. I kept the old one in the tank, but calibrated both.

They both measured the same PH in the tank, but once CO2 started they didn't drop at same rate.
Currently I have 6.4 and 6.7 readings?!

I tried doing a test with buffer and they are both accurate.

What could the difference be? Could there be this much difference in each side of the tank?
 

Zeus.

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but calibrated both.

Yes, been there both probes correct at 4.0pH and 7.0pH with buffer yet vary in between when in the tank. With pH being on logarithmic scale and probes being very sensitive and made to different specs I think this is inevitable.

But on the other hand do with need an accurate measurement of pH for our tanks? what advantage does knowing the actual pH yield? IMO/IMO none.

I don't even bother calibrating my probes anymore. The DC gives the approximate [CO2] and the probe tells me if its stable. If you have two probes in tank and one reads 6.4 and the other reads 6.7 form lights on till CO2 off +/-0.1pH what does it matter both are relatively stable so [CO2] stable. There is no magic pH level
 

kilnakorr

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But on the other hand do with need an accurate measurement of pH for our tanks? what advantage does knowing the actual pH yield? IMO/IMO none
You are right, and I don't really care about the specific PH. But when tuning in CO2, I'd like to know if the probes are reading right. They both measure same value in tankwater, but with CO2 injected they don't drop at same rate.

I'm starting to think, I have a PH goblin in the house messing up my readings...

PH of degassed tank water: 8.3
PH tank water in tank : 7.5
PH with CO2 (yesterday): 6.4

Looks like a 1.9 drop, so currently I really have no clue what PH to aim for:confused:
 

Zeus.

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PH of degassed tank water: 8.3
PH tank water in tank : 7.5
PH with CO2 (yesterday): 6.4

Looks like my figures ;)

Looks like a 1.9 drop, so currently I really have no clue what PH to aim for

Use the DC colour change. Once the pH is stable wait 2hrs from when pH did not change and the DC colour is the approximate [CO2] . If fish floating in tank your too high :eek:, fish swimming at surface or pass out when feeding - your close to limit. Snails all at top off tank - too high
 

kilnakorr

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If fish floating in tank your too high :eek:, fish swimming at surface or pass out when feeding - your close to limit. Snails all at top off tank - too high
I had 2 fish at surface yesterday, and a bright yellow DC, so might be a little to much.

Currently, doing a new profile and will aim / tune for 6.6

I also, recalibrated both PH readers again, so hoping they'll agree on the PH drop:)
 

kilnakorr

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Just to check there is no drift in the probe when I'm doing the profile, so just a double check. Last time I did it they was a difference of 0.4pH on the different probes
Makes sense.
Update: I now got 6.6 and 6.67 (6.6 and 6.64 when lights on 3 hrs ago).
I adjusted midway, as I could tell bps was to low to get there in time for lights on.
DC is lime green, and all fish are active showing no signs of stress.
Gonna do a new profile tomorrow, and hopefully my K2SO4 arrives tomorrow for a new batch of ferts.:)
 

Zeus.

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I adjusted midway, as I could tell bps was to low to get there in time for lights on.

Was you pH stable before you adjusted ( I assume you mean you adjusted the BPS/injection rate) if it was adjust it back and just shorten the CO2 on time before lights on.

Adjusting the BPS/injection rate will change the time it takes to get the pH drop but also changes the target pH and stable pH. Reach your target pH/[CO2] , get it stable and the drop time is the drop time ( unless you have duel injection/solenoids/timers)
 

kilnakorr

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Was you pH stable before you adjusted ( I assume you mean you adjusted the BPS/injection rate) if it was adjust it back and just shorten the CO2 on time before lights on.
Yes, it was pretty stable at around 6.8, or at least dropping VERY slowly.
Just checked and have 6.6 and 6.67, so been amazingly stable, for the last few hours.
Just need to see how long this takes, and maybe just add a little more, as it looks like I can push it a little more:p
 

kilnakorr

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Sounds like you have good quality pH probes/electrodes/monitors. Which ones are you using?
Yes and no.
My 'old' one is a milwaukee, with a €200 price tag.
Because of a facebook discussion, I came across a cheap chinese 6 in 1 measuring device for €65. Had to try it. So far so good, but if it will last more than 2 months is the question ;)
 

kilnakorr

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@jaypeecee It will. It has temp, TDS/EC and PH/ORP probes, so plenty of gadgets.
I accidently ordered another one, so I guess I can have both PH TDS and ORP EC running all at once:p
 

kilnakorr

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It's a tricky parameter to get your head around
I guess it will tell you if something starts slipoing in the tank. I guess we just want a good reading 300-400 and see it stable like many other things in the tank. If it starts to drop, something isn't right:)
 

jaypeecee

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Hi @kilnacorr
I guess we just want a good reading 300-400 and see it stable like many other things in the tank.

Speaking from my own experience, those figures (+300 to +400mV) are not easy to achieve. I suspect there are many tanks out there that fall short of this range. All it takes is a small amount of organic waste to drag these figures down towards the +200mV mark.

JPC
 
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