The Banggai Cardinalfish (Pterapogon kauderni) is a small tropical cardinalfish in the family Apogonidae. It is the only member of its genus. This attractive fish is popular in the aquarium trade. It is among the relatively few marine fish to have been bred regularly in captivity, but significant numbers are still captured in the wild and it is now an endangered species.
The mandarinfish or mandarin dragonet (Synchiropus splendidus), is a small, brightly colored member of the dragonet family, which is popular in the saltwater aquarium trade. The mandarinfish is native to the Pacific, ranging approximately from the Ryukyu Islands south to Australia.
If you heard about a tiny, funny-looking animal that spends its life floating upside-down on the surface of the Pacific, Atlantic, or Indian Ocean thanks to an air bubble which it swallows and keeps inside its belly, going wherever the currents and the wind take it, you would probably think it was just a harmless creature that likes to relax in the water. But this slender, up-to-3-centimeter-long animal, which is called the blue glaucus, blue sea slug, or blue ocean slug, is not nearly as innocent as it seems.