The natural position would be part of "The CO2 forms a pocket under the filter floss and continues to be dissolved into the water after the solenoid switches the CO2 off". I cannot predict how big a part but it shall be substantial as most of the water-flow will tend to go round the bubble. It would be much better if you use a simple Rex Grigg type in-line reactor on the return path of your aquarium.
Yes, this would be a problem. I intend to automate the CO2 injection with a pH probe and solenoid valve. Such automation would be pointless if switching off the CO2 didn't stop CO2 dissolving into the water.
Each of the sump dividers that has water going over is a spot for degassing but smooth flow, less drop and covering the sump should help as the CO2 is heavier than air and would stick around. I'd lose the dividers between D and E. The area where the pump is is where evaporation takes place and the more water in there the better...
I think this is a good idea. As I considered the sump layout I questioned whether I really needed to separate the equipment and the sump pump. I also questioned whether I needed a bubble trap in a fresh water aquarium. I can see a need in a salt water tank where foaming would be an issue, but I don't think this would be an issue in fresh water.
I don't know why so many people have trouble with reactors. I follow the instructions and both have worked just fine.
I think this is one of those times when the question is the answer. From my reading and obsessing over the CO2 reactor, I understand there are a couple of important variables:
1. The height of the reactor
2. The flow rate of water through the reactor
3. The water pressure in the reactor
I think it may be the case that people who fail fail on points 2 and 3.
Point 2 should be self evident (a higher flow rate pushes more water past each CO2 bubble). However, I think point 3 is the more interesting one.
A lot of posters talked about the importance of head pressure, and it seems the classic design calls for the CO2 reactor to be plumbed into the return line to the aquarium. This would have the effect of pressurizing the reactor chamber.
In accordance with Henry's law the solubility of gas in a solvent is proportional to pressure. See:http://chemwiki.ucdavis.edu/Physical...ility_of_Gases
. So it seems that a low powered pump simply returning the reactor water back to the sump might not be effective in dissolving the CO2.
With this in mind I have decided to persevere with the Cerges reactor. I intend to install a high pressure pump with a variable flow rate, and install gate valves before and after the reactor. This way I should have good control over the flow rate through the reactor and the pressure in the reactor.
Thanks to everyone for their help.