My DIY
I made a DIY reactor similar to the Plant Guild vortex reactor. I got a Rio 90 water pump ($7 online) and a nearly clear plastic jar. The airline goes through a hole in the side and jams into a kitchen scrubbie, actually half a scrubbie.
Might be better to not have the water pump directly above the jar, as with the power off the gas rises into the pump and airlocks it. I have to tip the unit over to clear it when I restart the unit.
It is a really efficient reactor, I'm getting a nice CO2 level with a very low bubble rate off my DIY CO2 generator.