[Delphinus]

Ah ok, that makes more sense, thanks!

I started off with a Milwaukee regulator/solenoid/needle valve/bubble counter combo but it's now been modded enough to be its own beast. Both the needle valve and the solenoid are swapped out now. I was able to unscrew the bubble counter from the needlevalve and I use a 1/8" hose barb from an old wooden airstone as the input, and it's just mounted to my wall next to the reactor.

I've been playing around with CO2 flowrate since yesterday and I'm getting closer to steady state but still not really there. The bubble rate isn't a nice steady rate, it goes more in bursts and then has a few seconds of nothing, which I think is probably from the check valve, so that's probably OK. Over a long enough period of time the bubble rate is still consistent. My challenge now is that it really doesn't take much of an adjustment (like, seriously, a small touch of the valve) to go from "the CO2 is too fast and thus the solenoid cycles off and on too much" to "the CO2 is too slow and the despite the solenoid being on the pH is just climbing higher and higher away from the desired set point".

I'm not quite sure how I can make this better. I guess one option is lower the regulator pressure and hope this gives me a bigger sweet spot for adjustments; and another is drill the reactor and get the pH probe inside the reactor chamber itself (right now the reactor effluent empties into a little capsule that the probe sits in - so the pH measurement is actually quite slow to react to whatever is happening inside the reactor).

The more I think about it the less I like not having the probe inside the reactor, so that's probably the next thing to fix..