Serpae tetra

The Serpae tetra is a member of the family Acestrorhamphidae, part of the order Characiformes. It is widely recognized in the aquarium trade for its striking coloration, which ranges from deep reddish-olive to a vivid scarlet along its flanks. A defining visual feature is the prominent, comma-shaped black spot located just behind the gill cover. Its dorsal fin is typically black with a thin white margin, while the anal and caudal fins display a brilliant red hue.

Taxonomy and History
The species was first formally described by the Austrian ichthyologist Franz Steindachner in 1882 under the name Chirodon eques. In 2024, it was reclassified into the genus Megalamphodus. The specific name, eques (meaning "horseman" or "rider"), is thought by some to reference the saddle-like mark found on its side.

Distribution and Ecology
The Serpae tetra is naturally found in a disjunct range across South America, including the Amazon basin in Brazil and the La Plata basin (spanning Argentina, Bolivia, Paraguay, and Uruguay). In the wild, it prefers slow-moving, vegetated waters, such as floodplain lakes and densely planted tributaries. It is highly adaptable and often inhabits anthropogenic environments like artificial ponds and reservoirs.

Care in Captivity
As one of the most popular species in the hobby, the Serpae tetra is generally robust and easy to feed, readily accepting flakes, pellets, and small frozen foods. Because they are schooling fish, they are significantly less stressed and display more natural behavior when kept in groups of six or more. Aquarists are advised to keep them in tanks with sufficient space and decor to provide visual barriers, which helps mitigate their occasional tendency to nip the fins of slower or long-finned tankmates. Most individuals found in the aquarium trade are captive-bred rather than wild-caught.