Have to thank our Russian friends for this one. After playing with the Rex Griggs reactor I wanted to try something else. Principal and cost are about the same design is different.
What you will need:
Omni OB1 Series A House Filter
2- 1/2" Male Threaded Adaptors with Barb end
2- 3/4" 90 degree Street fitting
2- 3/4" PVC Male Adaptor
2- 3/4" x 1/2" PVC Bushing
1- 3/4" CPVC Coupling - Note this has to be CPVC
as the PVC fittings are too big
1- 6 3/4" x 3/4" CPVC Pipe - Again has to be CPVC
and not PVC
PVC Primer and Cement
Teflon Thread Tape
Needle Nose Pliers
Drill and Drill bit for your CO2 Tubing
Total cost as ~ $23 each about the same as the Rex Griggs inline reactor if you don't use clear pvc.
Start by removing the Priming Button via the screw on the inside of the lid for the housing:
Drill out the hole to accept your CO2 tubing this hole shpould be smaller then your CO2 Tubing so it creates its' own seal.
Cut the CO2 tubing at a sharp angle so you can stick it through and pull it with the needle nose pliers. This should be slightly tough to pull through as it will create a seal as you pull the tubing through.
Cut the CPVC pipe off at 6 3/4", if you are using a different filter you may have to adjust the cut off length. I cut mine so it was about 3/4" off the bottom. Push the CPVC coupler over the nipple in the lid, should fit really snug. Then push the CPVC pipe into the coupler. I didn't glue this together as it was a snug fit and should be under little pressure.
Lay out and glue the fittings together, with the fitting I chose you won't need any extra 3/4" pipe as all the fittings go together.
Attach the fittings to each side jsut make sure you hook them up according to the Flow marking on the lid. Finished Product.
I will update tomorrow once I install these as to how effective they are, but based on looks they should function really well. According to the article I linked to about he got a .5 PH change in a matter of minutes.