Firstly, check that the aquarium has power and is not turned off. Secondly, look at the air pump in the hood or cabinet area and check that the 5mm airline tube is still attached. If this is all correct, then the please call the support team on 0845 3 904 903. The bubbles are not the main filtration pump and mainly for decoration so do not be too alarmed. We may be able to replace the airpump if we are in the area, or alternatively replace this on the next visit.