Now that you have built a CO2 generator, you need a CO2 reactor to mix all that CO2 in with the water. Here is how to do it. (stolen from http://www.gwapa.org/articles/inline_co2_reactor/
1) Go to Lowe's and pick up the following items (Home Depot didn't have everything):
1x 1-1/2" PVC pipe, 10"-12" in length
2x 1-1/2" PVC coupling
2x 1-1/2" x 1/2" PVC bushing
2x 1/2" x 1/2" nylon barb to MIP adapter
1x 3/8" x 3/8" nylon barb to MIP adapter
1x 1/4" air tubing coupler
2x tubing clamps
1x can of PVC purple primer
1x can of PVC cement
1x roll of tape dope
1x tube of silicone
Bio-Balls, ceramic filter media, etc.
Note: not all parts are pictured above, and some extras are there too.
2) Make sure all of the PVC parts fit together (dry fit) and that the ends are nice and clean.
3) Apply the purple primer to the ends of the PVC pipe and one side of the inside of the couplers.
4) Wait a couple seconds for the primer to dry and then do the same with the cement. Immediately insert the pipe as far as it will go into the couplings.
5) Repeat steps 3 & 4 to attach ONE of the bushing to one side of the pipe.
6) Fill the pipe with Bio-Balls/ceramic media. I had to force the Bio-Balls in so I basically had one Bio-Ball at each end of the pipe and ceramic media filling the middle of the pipe.
7) Make sure you are happy with what you have in the pipe because now you have to repeat step 5 with the other bushing.
8) Now give it a minute to setup and dry.
9) Choose one end to be the input for your CO2 (this should be the end from which the water will ENTER the device, as well). Drill a hole that is small enough that you will have to force the smaller barb/MIP adapter into it.
10) Force the smaller barb/MIP adapter into the hole you just drilled so that the threaded side sticks out.
12) I was able to force an air tubing coupler into the end of the smaller adapter and it fit snug, try to do the same.
11) Wrap the end of the barb/MIP adapters with the tape dope (enough to go around 1-2 times) and screw the adapters into the ends of the pipe. You will probably need a wrench to do this - snug them all the way.
13) Go around the smaller adapter with silicone to make sure it is air tight.
14) After letting the silicone dry over night, cut your tubing on the return side of your canister filter and hook up the ends of the tubing to your new reactor. Use the tubing clamps to get a good tight fit around the barb adapters.
15) Hook up your CO2 generator to the input of the reactor.
16) Turn your filter back on and watch for leaks. Tweek as necessary.
That should do it, good luck!
As a side note, I have been working on this stupid thing for like two weeks now. I have made countless trips to countless hardware stores to find parts that would work. I am sure I have spent way too much money on the wrong parts, so hopefully you don't do the same! I suggest you dry fit the entire thing before leaving the hardware store, otherwise you will probably be making a trip back![/img]