i have bubbles on my SB too. same type of bubble that in the william's pix. i started my tank in mid nov 2004. and the bubbles appeared since jan 2005. it stared from the front view of my tank and it spreads toward the mid of my tank cos i can see it at the side view. at first i don't know what it was and i stired the SB a liittle to clear some bubbles. however, the bubbles still appeared on the next day. the bubbles appear even when my lights are off. it could be nitrogen i guess.