I've an inline reactor with my canister also. I rarely get any kind of build up at all, just in the reactor, but that's why I have a valve to release any undissolved CO2. But my CO2 shuts off an hour before the lights go out anyway, so there is plenty of time for any undissolved CO2 to get all mixed up before the lights go out. If you got a canister filter and is thinking about an inline reactor, I say go for it, you wont regret it. Just make sure you have a long enough reactor for your filter.