Aphyocharax anisitsi, the Bloodfin Tetra, is native to the Río Paraná basin in Argentina, where it inhabits fast-flowing, cool, well-oxygenated rivers and streams. Its most striking feature is the dramatic contrast between its glassy silver body and the deep blood-red coloration of all fins — dorsal, anal, pelvic, and caudal — giving it an unmistakable appearance in the aquarium. One of the Bloodfin Tetra's most notable qualities is its cold tolerance; it can thrive at temperatures as low as 18°C, making it suitable for unheated aquariums in temperate climates or for aquarists who prefer cooler water setups. Despite this cold adaptability, it also does well at typical tropical temperatures. The Bloodfin is an extremely active, fast-moving schooling fish that spends most of its time in the middle water column. It is entirely peaceful and reliable with tankmates of all sizes, though it may nip the fins of very slow, long-finned species when kept in small groups. Keeping large schools of 10 or more is ideal and eliminates any minor schooling aggression by directing the fish's attention toward conspecifics. The Bloodfin Tetra is one of the easiest tetras to keep and is an excellent recommendation for new aquarists.
