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Re: [APD] dropchecker setup
> From: rader at hep_wisc.edu
> It appears that using pH & dKH to infer co2 levels is prone to error because it
> assumes all buffering [alkalinity] is being provided by carbonates. How prone
> to error? I have no clue.
Well, I now have one data point which indicates the old tank water pH &
KH method *drastically* under-estimates co2 levels! [In retrospect this
jives with past experiences with great o2 pearling from yeast setups and
poor o2 pearling with pH-controlled co2 injection.]
Before adjusting my pH, my dropchecker indicated 3-8 ppm co2 (pH 7.2-7.6
dKH 4.4) whereas my tank had pH 6.85, dKH 8.0 indicating 33 ppm co2.
After adjusting pH as per my dropchecker, I have a nice green dropchecker
solution where pH 6.6 and dKH 4.4 indicates 33 ppm co2; whereas my water is
pH 6.15 dKH 8.0 indicating 164 ppm co2. [Wow!]
"Log entries" follow.
Is this typical, I wonder??
Setup info: 20 gallon tall, 1 1/2 bags Eco-Complete (~3" deep), Flourish
Comprehensive, Iron and Excel at 75% of recommended dose, lighting via
27 Luxeon Rebel (like Cree XPG) high-output LEDs, 15 cool white, 12 warm
(about 30% more light than a modern 150W MH), 9 LEDs on for 12 hours, all
27 LEDs on for 6 hrs/day.
8am 03/30/2012 - pH 6.85 dKH 8.0 (measured in 1/4ths) infers 33 ppm co2
installed dropchecker with 4.4 dKH ref. soln.
1pm 03/30/2012 - dropchecker reads 3-8 ppm co2 (pH 7.2-7.6 dKH 4.4)
inferred effective dKH is ~ 2 (pH 6.85 dKH 2 = 8 ppm co2)
set pH to 6.35 (as per pH 6.35 dKH 2 = 26 ppm co2)
8pm 04/01/2012 - dropchecker reads 13-20 ppm co2 (pH 7.0-6.8 dKH 4.4)
inferred effective dKH is ~1.4 (pH 6.35 dKH 1.4 = 17 ppm co2)
set pH to 6.15 (as per pH 6.15 dKH 1.4 = 29 ppm co2)
8am 04/01/2012 - dropchecker reads 33 ppm (pH 6.6 dKH 4.4)
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