Hi, is anyone able to help me out with a CO2 system, I bought one of the Sera models and am wondering if I should have the airline (oxygen) running at the same time or am I negating the purpose of the CO2- any advice on the proper setup gratefully appreciated

Do not run oxygen.If you feel the need to run air into aquarium do so only after lighting has gone off at night and stop airation before lights come on in morning

Too much surface agitation will diffuse the CO2 in to the atmosphere. But if your plants aren't producing enough O2, then you'll need that agitation to keep the fish breathing.