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Cape Clear

Hmmm, co2 levels. When you ask how PH tracks through the photoperiod, I suppose you mean solely as measured by the drop checker? I'm not measuring it any other way.
Hi Paul,
In order to properly track a dynamic pH you'll really need to use a pH probe and record the data every half hour or so. The DC is just too slow and clunky to give you accurate data. Getting accurate pH readings will help you to assess the behavior of the gas. It may be, for example, that the pH reaches it's minimum (CO2 at it's max concentration) farther into the day than is optimal. So this will tell you that the gas should turn on earlier and can be shut off earlier. The instantaneous reading of the probe also can more accurately illustrate the effects of your surface agitation.
Or it could be an ammonia spike. I put in some new plants a month ago and didn't trim off all damaged material. As these parts decayed could they have caused such a spike?
Possibly. Another possibility is that if these were planted in the substrate then disturbing the substrate could also have kicked up ammonia. If you didn't do a water change straight afterwards that could have triggered it. It's very difficult to isolate the exact cause, so one has to assume all the known causes and fix each possible cause. Water changes as well as getting the CO2 right will address both possibilities.
Taking a step back (figuratively as well as literally), it's evident that there's now probably four times as much plant mass in there as in those healthy, early weeks. Maybe more. And more plant mass will need more co2
Correct!
So I've tweaked up the co2 injection rate.
Good, but get a quality probe so you can fix your gas on timing.

Cheers,
 
And more plant mass will need more co2.
Does it though?
Unless you’re providing very low levels of CO2 and very high plant mass (though growth rates may be slower than in a higher nutrient system), I remain unconvinced

Tropica seems to have run this aquascape fine with only 20mg/l CO2 (including some plants considered “high” light/CO2 demand)

 
Does it though?
Unless you’re providing very low levels of CO2 and very high plant mass (though growth rates may be slower than in a higher nutrient system), I remain unconvinced

Tropica seems to have run this aquascape fine with only 20mg/l CO2 (including some plants considered “high” light/CO2 demand)

I always laugh when I see the spec sheet on those tropica tanks; 200ml tropica ferts weekly!?! Hahaha
 
Looks like Milwaukee is a respected brand. Their ph600 pen is available for £15 - £25. As I'd presumably only be using this for a few days, to get a handle on injection timing and rate, that would do it I reckon.
 
Milwaukee is a respected brand.
er...uhmmm...
Can I convince you to splash out on Hanna (Instruments)

Definitely select one that can be calibrated, and can be done with preferably 3 “standards”, or at least 2 standards that bracket the region of interest (drawing a calibration curve through a single point can yield some pretty exciting lines)
 
Yeah, I have to admit, I'm a Hanna fanboy myself, but I recognize they are expensive. My personal favorite is the combination pH/TDS/Temp HI98129 which currently retails for (gulp) only 144 Euros...The do make pH only probes for considerably less, but never mind, Milwaukee is good too. Just make sure you have and always use the calibration fluids (7.0 and 4.0) and you'll be fine.

Cheers,
 
Too late, a Milwaukee has been bought.
In case you haven’t read this product page (good storage and usage tips)


Unfortunately there’s no real technical specifications included
 
Thanks for that, @alto - I've discovered that, infuriatingly, the pen doesn't come with any calibration/buffer solutions, and Sterner don't even nudge you in that direction when you order it! So I've now ordered some sachets separately.

I'm guessing calibration is only needed from time to time? I'll be using it repeatedly over a few days and then it'll probably not be used again for a while. I'm assuming, once calibrated, it won't wander off that calibration for days or perhaps a few weeks? I suppose I can find out whether it has drifted off by turning it on and sticking it in buffer when I want to re-use it, and see if it's still reading accurately.

Thanks again for all the assistance (and to @ceg4048) - much appreciated.
 
I've ordered ten sachets of ph7 solution, as it seems to be a one-point calibration process. Hopefully that'll do me for a couple of daily half-hour sets of data? Or do I literally need to recalibrate for each and every one of those half-hourly measurements?
 
I've ordered ten sachets of ph7 solution, as it seems to be a one-point calibration process. Hopefully that'll do me for a couple of daily half-hour sets of data? Or do I literally need to recalibrate for each and every one of those half-hourly measurements?
Hi Paul,
Single point calibration, really? OK, fair enough. Probably Darrel has a few posts regarding probe calibration. The probe's electrode outputs a voltage for each pH value and there is a theoretical straight line representing the voltage along which, ideally the probe outputs from 0 to 14. No probe follows the line exactly - they either drift above or below the line across the pH range. I would be guessing if I told you how much drift there will be in a half an hour. Maybe it will be fine, maybe not so fine.
The probe is an essential tool Paul. Yes, for this exercise you'll take some readings and then put the probe away, but a month from now there may be another issue in the tank and the probe will be useful to perform the same exercise. I don't consider the pH probe to be disposable because there is always something wrong with our CO2 and this is the most useful tool for getting to grips with the issue. In any case, even if it is only a single point calibration I would still get some 4.0 solution and after a rinse, dip the probe in it after the 7.0 calibration, just to make sure that it reads close enough to 4.0.

Cheers,
 
The probe and buffer sachets turned up yesterday, so I took some half-hourly readings.
I finished a 50% water change at noon, using my (pH7) tap water. pH readings as follows:
1300 - 7. 0
1330 - 6.7 (co2 injection begins)
1400 - 6.7
1430 - 6.7
1500 - 6.5
1530 - 6.4
1600 - 6.3
1630 - 6.3
1630 - 6.3
1700 - 6.2
1715 - (lights come on)
1730 - 6.2
The readings then stayed at 6.2 every half-hour until
2200 - 6.2 (co2 injection ends)
2230 - 6.3
2300 - 6.4 (lights go off)
2330 - 6.4
0000 - 6.5
0030 - 6.5
0100 - 6.5
0130 - 6.6
02.00 - 6.6
Then I went to bed.
This morning:
0800 - 6.8
0930 - 6.9

What have I learned?

Re. calibration, I repeatedly checked against several sachets of pH7 buffer during the process. I'll order some pH4 as well.
 
What have I learned?
Hi Paul,
Yeah, I'm finding this data really odd because in half an hour from 1300 to 1330 there was a 0.3 unit rise yet it required 2 hours of injection to have it fall by 0.3 units. You probably provided the information somewhere regarding your KH but it looks like the behavior of super high KH. In any case, if the probe is to be believed, there is no way it should require 4 hours to achieve a 0.5 pH unit drop.
Does the DC corroborate this data? Some of your photos show a lime green or yellow DC but it is unclear at what time of day that is. Either the probe is faulty or your injection rate is just a trickle and needs to be adjusted some more. What you've learned is to be suspicious about everything related to CO2 mate. Sorry. :confused:

Cheers,
 
So I've not re-done the Ph readings, primarily because it's such a pain to do. The staghorn continues, I've raised the luminaire a little more, and I'm focusing on propagating healthy new growth, with assertive pruning, rather than preserving existing growth, which is a fool's errand.

Just today introduced a shoal of black neon tetra - fabulous fish! The phantoms, as their name suggests, have always rather kept to the shadows, but the neons are bold and brilliant - love them already!
 

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