Green fire tetra

Aphyocharax rathbuni

Also known as Redflank bloodfin

FreshwaterFish

Care at a glance

Temperature: 72–79°F (22–26°C)
pH: 6.0–7.5
Adult size: 2 in (5 cm)
Minimum tank: 20 gal (75 L)
Temperament: Mostly peaceful
Social behavior: Schooling
Swim level: Middle
Difficulty: Easy
Breeding: Medium
Rarity: Common
Origin: Paraguay, Paraná and Uruguay river basins, South America (Brazil, Paraguay, Argentina, Uruguay)
Family: Characidae

Overview

Keep them in a group of at least six to eight, since a bigger school cuts down on nipping and brings out better color. They're active, hardy, and sit in the middle of the water column. Despite being mostly peaceful, they have a real fin-nipping streak, so they're not a fish for slow or long-finned tankmates. Skip bettas, gouramis, angelfish, and fancy guppies, and pair them instead with robust, fast-moving species. Run the tank from 22 to 26 C with a pH between 6 and 7.5. Feed small flakes, micro pellets, and frozen foods like daphnia or brine shrimp.

In the wild

Green fire tetras come from the Paraguay, Parana, and Uruguay river basins across southern South America, in Brazil, Paraguay, Argentina, and Uruguay. These are clear, flowing waters that cool off through the seasons, so they don't need tropical warmth. Give them a tank of at least 75 liters with a sandy substrate, dense planting around the edges, and open space in the middle for swimming. Add some moderate flow to suit the moving water they're used to. Keep them between 22 and 26 C, with a pH from 6 to 7.5 and soft to moderately hard water.

Good to know

This is Aphyocharax rathbuni, a characin in the family Characidae. Adults usually settle around 4 to 5 cm in the aquarium, though FishBase lists a rare maximum near 7 cm. It's an egg scatterer with no parental care, and a healthy fish lives several years. Most stock in the trade is commercially bred.

Did you know

They handle cooler water better than most tetras. The Argentine and Uruguayan populations live through seasonal temperature drops down to around 20 C, so this is one of the few characins you can keep in an unheated room temperature tank in many climates.