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Quick question around co2
- Thread starter jwmachon
- Start date
Hi all,
Cheers Darrel
They are slightly strange numbers, you would expect the pH to be higher and the dKH to be higher at that dGH level. What does the report from your water company say?
You can only use the chart when you have <"4dKH fluid in a drop checker">. This means that the pH of the drop checker fluid (indicated by the colour change of <"bromothymol blue pH indicator)"> is dependent purely on the CO2 that diffuses across the <"air gap of the drop checker">.
Cheers Darrel
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Tap water is higher but lower in tank, tap water is KH 8 and pH 7.5
What I mean is, do you use a pH meter (calibrated?) or a test strip, etc.
Tap water is higher but lower in tank, tap water is KH 8 and pH 7.5
Yes hanna calibrated this morning, also drop checker shows same
Andy Pierce
Member
I expect you have active substrate in your tank that is keeping the pH down and/or KH down? As others have said if your tank is in a stable equilibrium where dissolved CO2 is controlled by KH and pH and no other factors, your combination of KH and pH is not really achievable - the CO2 levels would need to be >30ppm which is 10x higher than "expected". If you just did a water change you can also influence these numbers because the pressured water in your tap is not in equilibrium with the external atmosphere (like your tank is).
That sounds more reasonable. I’m in Doncaster and my KH is around 8+, GH 13 and my PH is around 7.8 - 8.0. After co2 injection, my PH is safe around 6.8, below that the fish start gasping.
To get an accurate PH reading, leave your tap water in a cup over night and then test PH next day, you may find a slight higher PH reading. Same can be done with tank water.
Why do people test and leave it overnight then test when it's the tank that we keep confused with that bit lol
Out of tap it's 7.7 fresh
Yea ph out of tap is about 7.5 and tank 7':;-*£#;+@
Depends on what you are wanting to know, you had mentioned your tap water readings, so I thought I would state you can do this with your tap water also. But yes your tank water is the best to take the degassed measurement from, and to be safe think it is 24 hrs to fully degass and find a more true PH reading. You can then aim for the 1 PH drop (whilst watching fish closely, deop checker etc).
Correct
Hi all,
cheers Darrel
The "one unit pH drop = 30 ppm CO2" is a really strange one, have a a look at @Jose comments in <"Question about pressurised CO2 and water disturbance">.
cheers Darrel
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1 pH drop means 10x increase in the CO2. There is an assumption that in equilibrium, you would have about 3 ppm CO2 in water, but that depends on where you put your water (how many occupants are in the room), and how long you wait (and what dimensions the jar has). It will be somewhere between 1.5 and 4 ppm. You multiply that by 10, so you get CO2 in water between 15 and 40 ppm at 1 pH drop.
As Darrel says, the chart applies when you only have bicarbonate as a buffer in your water, which might or might not be the case. If your readings are correct, the only explanation would be that the KH test shows more alkalinity than just KH.
If you mean the drop checker with the standard solution (4 KH + indicator), then that indicates high CO2 levels. Without CO2 injection, I have no theoretical explanation for that, maybe in an enclosed system could be possible. Do you move your water with a filter or an airstone? Could you maybe post a picture, I am really curious what your setup looks like.
On second thought, if your tropica soil lowers the pH, the CO2 release from the bicarbonate must be increased. In this case, this all makes sense, and once the soil buffer is saturated, CO2 will no longer be produced. I am surprised about the magnitude of this effect, though.
Mat H
Member
Think you're correct, I had a similar thing happen [also Tropica substrate] i.e. I needed a major recalibration of CO2 once the substrate effect had subsided wich was somewhat sped along by 50% changes every other day for a couple of weeks.
Initially I was confused as to why I was suddenly struggling to get a sufficient drop / lime green drop checker and then realised that it was probably the substrate.
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_Maq_
Member
Still, there seems to be something wrong about @jwmachon 's measurements.
Aqua soil releases protons and binds metal cations (presumably Ca2+) in their stead. Subsequently, protons change bicarbonate ions into H2O+CO2 (H2CO3).
That is what aqua soils do. CO2 may get oversaturated. If significantly, well, then we should see significant decrease of Ca content (GH) and alkalinity (KH).
Well, there was 1 dKH drop (8 in the tap water and 7 in the aquarium), and 1 dKH equals 0.357 mmol/l bicarbonate, from which 0.357 mmol/l (15.7 mg/l) CO2 is released. If the system was closed, this 15 ppm would be the concentration after 1 KH drop, but I assume it is not closed; some CO2 dissipation must occur. One thing that complicates the equation is that if buffers are released from the soil into the water, that will add to the measured KH, so the real drop in bicarbonate concentration could be higher. Still, we probably still need some inaccuracy in measurements to get the values from this tank.
Right recalibrates meter
Tank water 7.3
KH 7
GH 10
Degassed tap water for 18 hours 7.8
Degassed tank water for 18 hours 7.4
Did a water change yesterday using 50/50 ro
Those results look better
Am I now right in thinking I should be looking for a pH drop to 6.4 injecting co2
Tank water 7.3
KH 7
GH 10
Degassed tap water for 18 hours 7.8
Degassed tank water for 18 hours 7.4
Did a water change yesterday using 50/50 ro
Those results look better
Am I now right in thinking I should be looking for a pH drop to 6.4 injecting co2
