Bloodfin tetra

Quick facts

Adult size

5.5 cm

Lifespan

can live up to 8 years

Tank zone

mid

Temperament

peaceful

Difficulty

beginner

Schooling

recommended 8+ (critical minimum 6, thrives at 12+)

Water parameters

Temperature

18–28°C

pH

6.0 to 8.0

Hardness

2 to 20 dGH

Tank requirements

Minimum volume

80 L

Minimum length

75 cm

Flow

moderate

Lighting

moderate

Substrate

any

Open swimming room

needed

Lid

required - jumper

Feeding

Diet: omnivore, feeds primarily at the mid.

Eats anything offered without hesitation. Flake, pellets, frozen bloodworm, frozen brine shrimp, frozen daphnia, live daphnia, blanched vegetables. Not particular about feeding zone; takes food from the surface, midwater, and will even pick at items on the substrate. They're fast feeders that get their share in any community tank. The red fin coloring intensifies noticeably with a varied diet that includes frozen or live food at least a few times a week. A straight diet of dry flake produces dull fin color. Feed twice daily in moderate amounts. Overfeeding is hard because they burn calories through constant activity.

Compatibility

• More active and slightly pushier than most small tetras. In groups under 6, bloodfins get nervous and redirect that energy into nipping tankmates. Groups of 8+ settle the hierarchy internally and leave other fish alone.
• Not suitable for long-finned species. Bettas, fancy guppies, and angelfish will get their fins picked at. Short-finned, robust tankmates are the right pairing: other barbs, danios, larger tetras, and catfish.
• Cold-tolerant for a tetra. Survives temperature drops into the mid-teens Celsius that would kill neons or cardinals. This makes them one of the few tetras suitable for unheated indoor tanks or subtropical setups alongside white clouds and peppered corys.
• Will eat adult cherry shrimp. Not reliably shrimp-safe despite sometimes being listed as such. Small shrimp species and shrimplets are definitely food items. Keep them out of dedicated shrimp tanks.

Habitat

Native to the Parana River basin in Argentina, extending into parts of southern Brazil and Paraguay. This is a subtropical region with seasonal temperature variation, which is why bloodfins handle cooler water (down to 18°C or even lower briefly) better than most tropical tetras. Found in slow to moderately flowing streams and river margins with sandy substrates and bankside vegetation. The body is silvery with a blue-green iridescent sheen, and all fins show some degree of red coloration, with the caudal and anal fins being the most vivid. Males are slimmer and show brighter red; females are deeper-bodied and slightly duller. The species (Aphyocharax anisitsi) was first imported to Europe in 1906, making it one of the oldest continuously available tropical fish in the hobby. It fell out of fashion in the mid-20th century as flashier species became available but has never disappeared from the trade. Still commercially bred in large quantities because it's cheap to produce and nearly impossible to kill. Adult size is about 5.5 cm. Lifespan can exceed 7 years in decent conditions, which is long for a small tetra.

Breeding

One of the easiest tetras to breed. Unlike many South American tetras, bloodfins don't require soft acidic water to spawn. They'll breed in moderately hard, neutral water without issue. Condition a pair with frozen food for a week, then move them to a breeding tank with spawning mops or fine-leaved plants. Temperature at 24–26°C. Spawning occurs at dawn, typically within a day or two of introduction. The pair scatters 300-500 eggs among the plants and substrate. Eggs are semi-adhesive. Adults eat every egg they can find, so remove them immediately after spawning. Eggs hatch in 24-30 hours. Fry become free-swimming in another 2-3 days and take baby brine shrimp as first food. Growth is fast for a tetra; juveniles show fin coloring within 4-5 weeks. The combination of easy breeding, tolerance of varied water conditions, and large clutch sizes makes bloodfins a good first breeding project. Commercial breeders produce them in outdoor ponds by the thousands.

Common problems

Among the hardiest tetras available. Serious disease problems are rare in established tanks. Ich appears occasionally in stressed new arrivals; standard treatment works without complications. The main behavioral issue is nipping in small groups, which is easily solved by keeping 8 or more. Jumping is a concern; they're active near the surface and will exit through any gap. A lid is necessary. Color loss in the fins usually points to dietary monotony; add frozen or live food to the rotation and the red returns within a week or two. Aggression toward slower tankmates (gouramis, bettas) is a compatibility problem rather than a health problem, but it still results in stressed, damaged fish. Match them with species that can handle the pace.

Bioload

Bioload coefficient: 0.6 (small active tetra; slightly higher than neon due to greater activity).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size