you cant have too much oxygen to the roots, the more the better, but if you dont know what CO2 does for the plant, you probably shouldn't be using it. CO2 is for the green leaffy parts of the plant not the roots, and if you are not familiar with CO2 injectons systems i wouldnt worry about even atempting this. so short answers- as much Oxygen as you can get but no CO2. good luck. id love to see pictures of the lettuce system. ~Ryan

no ten gallon pools inside your first try.

CO2 Is NOT needed and i think you have that confused with o2 (oxygen)
co2 only benefits certain plants in controlled evironments. (usually commercial greenhouses)

For what you want to do i suggest 5 gallon buckets or even smaller with lids (not transparent) and cheap walmart fishtank pumps supplying the roots o2.. you can use airstones or make your own using soakerhose, etc.

plants can be grown "Aeroponically" as well. This is where fog or sprinklers (or flood and drain etc.) come in.. There is a lot to learn but the principle is simple. Do some simple research.

scroll this forum for ideas not some catalog, it's throwing you off. They (at least my local hydro store) try to make it seem like you need everything from CO2 to their house brand nutrients. Don't believe it. try the sponsers here for net cups,Fired-Clay pellets,Horticultural Rockwool,meters and testers etc.

common air aproxamately 73%nitrogen 20% oxygen 3-4%carbon dioxide the rest traces of other impurities. Bubling air to the roots works fine no need for oxygen tanks. carbon dioxide is actually not needed or wanted at roots but the 3-4% in air seldom causes any trouble.raft is the easiest cheapest sytem for letuce. aeroponics is the most critical as it can cause death quicker on failure than any other system. Misters and mineral laden water is not the most reliable mix. the kiddie pools are actually not a bad idea we had a local ag office do one last year. you get a few plants that way a five gallon bucket is way to deep and small in surface area you could only get 1-3 plants. make sure the aquarium pump is above water level and use a bubble curtain or if you are cheap just make a big loop of aquarium tube and poke holes in it with a stick pen heated in a candle or lamp. you need some type weight or atachment to keep the bubbler at the bottom. you should be able to raft lettuce in 3-5 inches of water but over 8 would really be a waste better to use less water and change it once or twice when it is spent. http://edis.ifas.ufl.edu/HS184 is from a florida university and it is aimed at children and first time hobbyists just liike yourself they did not even bubble the water.I believe they also showed a sytem of 4x8 foam and 2x4's lined with plastic sheet for about 30 or so plantsites. these seem like generouse spacings to me mel bartholemew in square foot gardening gives 4 lettuce per square foot if i remember right. If you can't find orhid pots or baskets you may be able to improvise with a small hole and a cotton ball or a fruit basket from the grocer or some plastic cups with lots of large holes drilled or burned into them.