2. price. Compared with butterfly glue, grouper glue is more affordable and easily accepted by the public. Gelatin is the dried product of swim bladder (the organ used by fish to adjust the ups and downs, also called fish bubble, which contains gas). Rich in gum, it is named fish glue, also called fish belly flower glue. Fish glue is as famous as bird's nest and shark's fin. It is one of the "Eight Treasures" and is known as "Marine Ginseng".