Are you talking about the feces? Stress can sometimes cause total evacuation of the bowels and result in a slimy clear mucus to be produced for a short time but many cichlids carry a low level hexamita infection that can also get worse if the fish is stressed. Metronidazole in food will cure it, It is not harmful to any fish that I know of and won't harm your BB, many discus growers use it a s part of routine rearing.