airline efficiency : combining air with CO2

Any time you agitate the surface of the water you are losing C02 so it would be counter productive to use air also....when you inject C02 do the bubbles just rise to the surface, if so its doing no good, you have to dissolve the C02 bubbles in a reactor. Google search power C02 reactor and you should get some good ideas on what you need.

Seaman - I've done DIY CO2 with a bubble wall. It's not efficient, I'll give you that, but it does work - you just need a lot more CO2 for the same effect. I can't see using a reactor in a 1.5g
I have to agree, injecting air to create surface agitation is going to flush out any CO2 that makes it into the water - if the air is being used to circulate the water through a small 'betta bowl' type UGF, that's a very tough problem to solve.
Misa - A while ago I wondered if it would be practical to attach my DIY CO2 line to the venturi on my canister filter's spray bar. I was warned that anything that will 'pull' CO2 into the tank may collapse soft soda bottles and draw the solution into your tank. I read up online, and you do NOT want this to happen, it's a nightmare to clean up and not good for the fish! I'd stay away from any method that puts any pressure on the line, in either direction (if you're using an airstone, make sure it's kept very clean - a clogged airstone causes back pressure, and can make your bottles exlode). DIY is great, but from all I've been told it needs to be treated with quite a bit of respect.