I run airstones in most of my tanks. I'm sure you guys realize that these don't actually oxygenate the water. It's the surface disturbance that does it, I just thought I would throw that out in the air.
vyasa: I'm not sure who told you that, but it's not entirely true. It all comes down to the fish, imo. Fish like Tigrinus and most Pims thrive in well oxygenated, fast moving water. Powerheads, airstones, etc, are a must. Discus on the otherhand prefer very stagnant water. I make sure all of my filter tubes are underneathe the water and there is very little current in my discus tank. Correct me if I'm wrong, but warmer temps=greater o2 content.