I like the design. I will comment on 2 two things:
1 Needs Work:
The rigid airline poked thorugh and glued is a bitt too flimsy. While attaching the airline, I wiggled it too much... and after a few hours of runtime, developed a very, very slow leak. So, I'm installing 3/16" brass barbed splicers. Rigid airline will attach to the splicer with a 1/2" section of soft airline tubing... on both sides of the reactor (inside/outside).
Here's the fitting upgrade..
So, I'll make two observations regarding this DIY CO2 Reactor.
2 Perfect:
It's so quiet. No whistling, no splashy noises... just silence... With my high flows, it drives off the collected air on startup in about 15 minutes.... just clear, silent water.. (I like that I employed a bit of clear PVC so that I can see what's going on inside of it!!).
It's a very good design. With my increased flows, compliments of 1" plumbing, I saw my pH drop .5 points in about 2 hours. Which I thought was incredible fast accross 5 tanks and my dual chamber sumps (effectively 7 x 20 gallon long aquariums). Picked up a new 20 gallon long today, so preparing to add the 6th and final display aquarium to the system.... My pump, filtration, reactor and UV are all scaled for it!!!