[Yokomo99]

I have a 135 gallon tank and I use a 500gph mag-drive pump and an Aqua-Medic 1000 inline reactor for diffusing the CO2. I am in Canada and a refill of my 10lb tank also costs about $15. You would only need to add the Aqua-Medic 1000 to the output of one of your filter canisters and you would be good to go.

 

[Yokomo99]

Here is a couple of pictures. Excuse the mess it is a work in progress.
The tank and regulator are on the left and the yellow tube runs to the reactor on the right.


This one shows the pump behind the tank.

 

[Yokomo99]

The Canister filter is not in the CO2 loop. The route is; Left end of tank ---> pump ---> reactor ---> Right end of tank.