See if the bubbles are truely coming from the plants. If so they will be very evident after 10 to 12 hours of photosynthesis (10 to 12 hours after the lights have been turned on.) Do you have them first thing in the morning??? If not, then the bubbles are prolly oxygen, the result of photosynthesis, especially if you see the bubbles after at least a few hours of lighting. It could be the sand, but bubbles from the sandbed usually bubble out during the period just after filling a tank (trapped air) or after 4 to 6 months as the sandbed megins to mature and the anaerobic bacteria begin to strip Oxygen molecules off the nitate in your tank and use the oxygen in their metabolism, releasing nitrogen gas to complete the
nitrogen cycle in the tank (this is the major benefit of deep sandbeds, they and a sufficient supply of Live rock contain anaerobic areas that allow obligatory anaerobic bacteria to complete the nitrogen cycle in the tank and release the nitrogen as gas (the bubbles escaping from the sand...) Hope this helps, let me know if you need more info!
------------------
Tom <"{{{{>(
(TDWyatt)
Wise men talk because they have something to say; fools, because they have to say something. -Plato
