Which Plants Produce More O2 ??

Hi All,

I have a 30 gal freshwater tank with a Fluval 203 cannister filter, and no
UGF. I have approxiately 15 small fish (ie. tetras, pleco, cory cats) and
two rather large amazon swords. I would like to put in another variety of
plant, but my concerns are my O2 content of my water. I chose the amazon
sword not only because I believe it to be hardy, but I also (perhaps
wrongly) believe that with the broad leaf variety, with the greatest
surface area, it would produce the most O2 ?

I have two pieces of driftwood in the tank as well, and I was thinking
perhaps something that would attach to the driftwood ?  I would like it to
'blend' into my theme of a slow running South American river setting...
and am not sure whether I could include a more 'colorful' plant... perhaps
some red in it, or some such other color? 

The list's help in my quest would be greatly appreciated.