Then I recommend going with either the Rex Grigg or Cerge style reactors, because either one will connect with the outflow of a canister filter. Cerge's style reactor is known to need a high gallons per hour rated canister filter because of what's known as flow back caused by the design, whereas the Rix Grigg style reactor doesn't have this design flaw, and I've ran one with a Eheim 2213 without any issues. The best thing about these reactors is no visible airline tubing in the aquarium because they are built to have the co2 injected into them directly.
The Rex Grigg design is a do it yourself co2 reactor built using PVC piping, here's a link to directions on how to build one...
http://www.rexgrigg.com/diy-reactor.htm