I have a RBTA that is about 12" across when fully extended in the day and he never bubbles anymore. When I first got him, he was really far down in the tank under T5s and bubbled and was very compact. In his current home, he's under 300W of LEDs, and maybe 6" under them, and he does not bubble, but is HUGE and hosts my large 3" saddleback.
The nem eats like a pig, is so super sticky, and healthy as could be. To me, it seems like bubbling or not means little to nothing about anything.