I'm not a high-tech guy, but I've only heard one way to maintain high levels of both CO2 and oxygen. You do the usual things to boost oxygen (surface agitation, airstone, etc) and bump your CO2 injection to compensate for the additional loss.
What filtration are you using? Since you don't like the look of an airstone you could drop it into the back of your HOB if you have one. For a canister, I read one forum member injects CO2 into the canister inlet so the filter floss catches the micro-bubbles. You could probably do the same with air.
For what it's worth, Cory of Aquarium Co-op did tests with a dissolved oxygen meter and found airstones to be by far the best means of oxygenating a tank.