So the rates of change in the reactor were measured.
The CO2 went up in the sump once the water stopped flowing in, but got NOWHERE near the CO2 saturation most have claimed.
Since the sump recirculates the CO2 reactor water, it's typically about 6.3 pH when the filter is running water through it, and about 6.5 in the tank.
when the filter was shut off, the level was 2" inches down, about 1 hour later, cramming a lot of gas in there(500mls per 2 minutes)?
10 inches
That's a lot of gas and cannot be due to impurities in the CO2 supplies.
The pH dropped to about 5.6-5.7 after 30 minutes and it tooks another 30 minutes to drop to 5.5.
Why?
I thought CO2 dissolves in a few seconds like 5 seconds according to many people?
Why?
Apples and Oranges.
They are comparing a bubble as it SLOWLY floats up at low CO2 concentrations.
This system is blasting the CO2 and the CO2 concentration is high.
Gas or any chemical flux follows Fick's 1st law of Diffusion:
J = -DA (Delta)c/(Delta)x
Where
J=Net rate of diffusion (gms or mols/unit time)
D = diffision coefficient for the diffusing solute
A = area of the membrane
(Delta) c = concentration difference across the membrane
(Delta) x = thickness of the membrane
Since the concentration changes and changes a lot inside the reactor, more is not being dissolved to that 2" level and the gas gap inside increases.
This slows the gas's rate of diffusion into the water.
It has to and Fick's law describes that it will.
So what happened when I restarted the filter again?
What do you think?
The gas bubble inside the chamber rapidly(about 4-5 minutes) dissolved into the water the level went from 10" back to a little under 2".
Difference? Concentrational changes alone.
This could not have changed:
1. D = diffision coefficient for the diffusing solute
2. A = area of the membrane/cross sectional area
This did change by a large factor:
3. (Delta) c = concentration difference across the membrane
This did not change:
(Delta) x = thickness of the membrane
So there's another issue going on, according to some aquarist, they claim that the saturation point for CO2 in water is 1500ppm or thereabouts.
This is true, but they forgot a very important factor in this statement: the rates of degassing.
If I have a nice wet/dry filter with air vents, I can dissolve a lot of gas into water without ever building up much CO2 ppm.
Yes, it dissolves, but never accumulates.
In a tank without a wet/dry filter and/or modified to minimize degassing, this will have a very different result, even though the gas and tank volume are the same, let's assuem the other stuff EXCEPT the degassing part is similar.
What goes in, must come out, if the gas is NOT dissolving.
This is a 2 box model.
So while we can say things about the maximum CO2 ppm water will hold theoretically in a sealed system, reality if quite different.
Our aquariums are degassing CO2 and like Fick's 1st law, the higher the concentration in the water, the greater the flux OUT of the water.
So the CO2 does not reach 1500 ppm easily and likely never even comes close in my own tanks. It's starting to degas MUCH faster as the concentrations rise.
Wet/dry chambers and reactor chambers are similar, the gas in solution will degass more as the ppm's increase.
If you suddenly add fresh "unstale" water as Matt suggest, this gas will quickly dissolve back into solution.
So Fick's 1st law applies in BOTH directions, dissolving and degassing.
Since degassing rates will be different for every tank, this is a tougher issue to pinpoint.
This build up of gas in solution and degassing in also not linear, it's exponential as time increases, it gets harder and harder to hit the 100% saturation level.
Again the Fick's 1st law predicts this.
O2?
It's tough to dissolve into water.
And there's not much of it, and certainly not enough to cause such dramatic changes inside the reactor in the sump test.
You can use cold water and sump and this will add super saturation levels of O2 also to see if the reactor will degas O2.
Then warm it up before turning on the filter pump again.
I do not think there's enough O2 to do what I saw, you might be led to think this over the course of the day as a few hours of higher than 100% are reaches in the water.
Again, a 2 box model, as some goes into solution, O2 is going out. But 1-2 ppm vs say 50 ppm? That's a much larger difference.
And CO2 easily changes that much if you add it only during the day light cycle.
O2 only changes 1-2 ppm. This seems like a more logical approach than claiming the CO2 magically dissolves in a few seconds, observations clearly show something else is going on.