I have a 65 gallon planted with a eheim 2217 canister. I recently purchased the automatic co2 system from Aquariumplants.com. I love it. I love it. Did I say I love it. it keeps everything right where I set it, totally automatic. It comes with the reactor that attaches to the canister very easily. I installed the whole thing in less than a hour. They were great on the phone with me the anytime I had a question. This is sounding like a commercial for them but I really like the system.