A lot of this depends upon the rest of the filtration system.
If your using a sump and skimmer, your going to get plenty of gas exchange from that alone, so breaking up the water surface is not necessary. If your using a canister filter, for example, it's a sealed unit so there is little gas exchange.
If it really bothers you, it's easy enough to add a second small power head just to break up the water surface. Ideally it should be placed as far from the filtration system intake as possible.