Analysis of information sources in references of the Wikipedia article "Discus (fish)" in English language version.
…Discus fish, pre-bagged for a quick sale, occupy a seller's shelves…Each tiny shop or stall usually specializes in a particular breed or category of fish or aquarium—some showcasing colorful but delicate discus and angelfish…
A special case is the discus fish, a cichlid Symphysodon discus, in which the skin of brooding fish hypertrophies and secretes mucus ('discus milk') which is eaten by the fry