• Scientific name: Exodon paradoxus
• Synonyms: Hystricodon paradoxus, Epicyrtus exodon
• Common name: Bucktooth Tetra
• Group: Characins
• Habitat: South America; Guyana - in the Rio Branco river, and Brazil – in the Amazonas.
• Size: 15 cm
• Biotope: Inhabits the rivers that flowing through savannah-like grassland and has sandy bottoms.
• Social behavior: Active and very aggressive characins. They are not suitable for a community tank, as they will attack any tankmates, stripping their scales and fins very quickly. They will attack even the larger predatory fishes. Fish without scales, like loaches, or armored catfish species usually left alone. Always keep them in a larger group, because they tend to attack weaker or smaller conspecifics when kept in smaller numbers. Also buy the entire group at the same time as new additions are usually attacked.
• Diet: Omnivorous; In nature they eat aquatic invertebrates, smaller fish, and the scales of other fish. In the aquarium they will accept live and frozen meaty foods, and will even accept dried foods too. Bucktooth Tetras are violent and greedy feeders.
• Breeding: Rare in aquarium.
• Tank: Minimum 150 litres
• Population: 12-20 fish for 200 litres
• Decoration: They like some water current, and their tank can be decorated with driftwood branches and roots. Use sandy substrate. They look very good in a densely planted tank.
• Temperature: 23-28 °C
• pH: 5.5-7.5
• Hardness: 1-20 NK°
• Lifespan: 6-8 years

Description: Exodon paradoxus has a typical elongated tetra appearance with a yellowish-brown body and 2 distinct black spots. The first spot is just in front of and below the dorsal fin, and the second is on the caudal peduncle. The dorsal fin is bright red. Under certain light conditions the metallic sheen of the body often reflects blue and purple iridescence. Interestingly in their natural habitats the local people place dirty dishes into the water and the Bucktooth Tetras perform a useful task by picking every piece of food from them! Exodon paradoxus has serrated lips with powerful jaws for its size, and these allow the fish to rip the scales from other species. It is an ideal choice for those wishing to keep a large shoal of a predatory species.

Males are slimmer and have slightly elongated dorsal and anal fin rays. It is possible to breed them in an aquarium. A separate breeding tank should be used with around 60x30x30 cm in size with some clumps of fine leaved aquatic plants on the bottom, or cover the base of the tank with some kind of mesh that prevent the adult fish from reaching the eggs. Before breeding, feed the fish with a variety of live foods and breed them in pairs. Spawning can be initiated by performing a large (50%) water change with slightly warmer water. The parents should be removed after the spawning. The eggs hatch in 2-3 days. The fry can be fed with small live foods, but cannibalism will probably occur, so move differently sized fish into separate tanks.