So assembly is very easy as are drilling two to three 3/16" holes.
As you can see from the pictures, we drill two holes on the top.
You insert a 12" long piece of rigid 3/16" tubing and glue the top and bottom with the PVC glue. This seals it in place and is the CO2 inlet.
I chose clear PVC(available through Aquatic Ecosystems) so I could use this like a bubble counter. I can see how many bubbles per second are going into the reactor.
The other hole can be used for two different functions.
It merely has a 3 " piece of rigid air line tubing inserted and glued in place.
It can have a simple ball valve(irrigation drip valves work well here) and allows you to remove any gas build up manually. It also allows control of the gas being sucked out if you want to use this for degassing the chamber with venturi suction.
This prevent any gas build up inside the venturi External reactor.
Another hole can be drilled, about two inches from the top of the reactor. This can be fed to the suction side of the powerhead to degas the chamber once the gas builds up to this preset level.
The usefulness of this method is incredible. Degassing the chamber via the venturi
loops allows the chamber to have much reduced gas lock and backpressure, as well as providing a fine gas mist once the gas buld starts affecting efficiency.
This waste some gas later in the day but adds the mist directly to the tank and plants. The effect is phenomenal.
This design is based on a closed loop like the internal venturi reactor.
Both are 100% efficient until the gas starts to build up and then it starts degassing the bubble into mist and ejects it out into the tank later in the day.