VaughnH;27812 said:
If the volatility or transient nature of CO2 were a big contributor to the variations around the tank, there would be a major gradient from top to bottom, because the loss of CO2 would occur at the surface, depleting that layer, leading to the gradient.
I wonder though, it seemed that the flow and exchange in the plant beds was lower based on CO2 meter readings.
CO2 is much larger an issue than say NO3, which plants can store and hold large reserves in their vacuoles, carbon as well, but not as CO2. I mean that in a short time frame, the CO2 can change by a very large amount. Seems the CO2 gradient is current and plant driven here.
Plants reduce the current and thereby exchange of CO2.
The demand for NO3 is much less, but it may still certainly occur and does in some systems according some research.
More current(up to the point, not more than say 2 mph) is good and reduces the boundary layer, so that not only CO2, but also NO3, PO4 etc get to the plant easily.
The CO2 mist and micro bubbles might break this boundary layer up and add more CO2 to localized regions(you can see the gas going into the plant beds).
This confirms the CO2 mist theories I've had as well...............
Some claimed it was homogeneous throughout the tank.
Yet once again these same folks and critics
did not bother to test or devise a test to see if their claim or my own was valid or not. I'll let the evidence and the test stand for themselves.
In the meantime, crow shall be served to the critics.
Perhaps the calibrated meter and the settling time at each data point was all wrong?
I doubt it.
Done this and taken plenty of gas readings for O2 as well to get fooled here.
So perhaps my tanks (all 5 of them and a client's tank) are different due solely to chance? 6 replications seems pretty unlikely for that to occur.
Maybe the high light tanks and the venturi mist played some role, I do not doubt this, but if you are going to see a variation, adding high current and an very efficient and responsive CO2 delivery method seems wise to get the most effective result.
At high flows, we would expect to see
less differences between the water column in the open vs the plant beds. Or with poor responsiveness from the CO2 delivery system. Or at low light intensity and low nutrient levels.
So you can see how to
slant the set up design to favor and rule out other possible interactions? Much like using EI to rule out nutrients as a limiting factor. What other things might cause poor CO2 uptake in plants?
Then go about ruling everything else out, step by step.
If the variations in CO2 in the water are due to plant usage of it, then the usage of all of the nutrients would cause similar variations in all nutrients throughout the tank. Doesn't that have to be true? Is another factor the changing state of the CO2 - from disolved CO2 to carbonic acid to carbonates and back and forth? I have no idea how dynamic that transformation is.
Perhaps, but the plants cannot store that much CO2 say relative to N, P, K.
This is even more true in limiting or leaner system, so what might this mean then? .........something to ponder...........
I do not think the state of H2CO3[aq] CO2[aq] is really an issue, it'll equilibrate pretty fast in our system.
Why? Because about 400 CO2's for each H2CO3 is present for the ratio of Carbonic acid to CO2, this why CO2 is a weak acid, most is in the form of CO2.
Our blood seems to have no troubles at high rates, nor fish blood, we are adding a lot of CO2 as well to keep it "stable" also.
Regards,
tom Barr
Regards,
Tom Barr