[ray-the-pilot]

Is this the reactor you are using?

http://www.aqua-medic.com/reactor_1000.shtml

Mine works really well and is very efficient. My reactor is on the outflow of my filter outside of my tank. I've noticed water going back to the check valve but there is no problem with back pressure. I don't have a needle valve. I use this regulator (the cheaper one):

http://www.aquariumplants.com/AquariumPlants_com_s_Electronic_Co2_Regulator_p/co2.htm

 

[ray-the-pilot]

I looked up your reactor and it recommends using it with a pH controller, which I have. I do not have a needle valve, solenoid valve or bubble counter in my set up. These three things are included in the regulator (all electronic). It works perfectly without any problems. I’d definitely recommend it.

 

[ray-the-pilot]

You are right about those 180 deg turns but not about the crud build up. I only notice crud building up in the corrugated tubing that Fluval uses. If you use standard smooth wall tubing, you do not get that strange build up.

Basically I run the outflow of my Fluval 405 strait into the top of the Aqua Medic reactor. CO2 pumps into the bottom of the reactor and floats to the top. The CO2 keeps recalculating in the reactor until it is completely dissolved (ie. 100%). If you use an uncontrolled amount of CO2 all of it will be dissolved in your tank and that could be a problem. That is why you need a pH controller. When the level of CO2 gets too high in my tank the controller shuts down the CO2. It very accurately controls the level of CO2 to within 2-4 ppm. If you are not going to use a pH controller, then I wouldn’t recommend any in-line reactor as a blip in your needle valve could cause radical (ie lethal) changes in your tank CO2.