best way to add oxygen to a tank.....

[RonR.]

hard plastic wide-jet pipe either pointed slightly under the water to get good water movement or slightly above to get the bubbles. Like this one about half-way down the page:

http://www.eheim.com/base/eheim/inhalte/index96a2.html?key=liniendetail_27655_ehen

The air diffusor looks pretty interesting.

Best of luck.