Kurt S. Adler Replacement Light Bulb (3 pack) (87474 / 3PK BLK/ORNG HW BUBBLE REPL BULBS (R0142))

If the bubble light needs assistance to bubble, let the light warm up for a little bit. Then, tap it lightly with a ruler. That should make the bubble action work. If this does not work, after the light has warmed up, you can also turn it upside down and shake it.