My tank has been cycled since Feb. of this year and I just started noticing bubbles a month ago. I have no idea if that is a long time or normal though.
depends on the quality of the sand. if you purchased truly live sand the bubbles should develop almost immediately. if not it does take awhile
good luck
jon
The nirtates in the DSB will turn to nitrogen gas...one of the benefits of a DSB. That gas will form into tiny bubbles that will occasionally release from the sand and float to the top of the tank. Mine happens alot when fish or inverts are messing with the sand.