Bloodfin tetra

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: any.

Behavior

Plant interaction: plant safe.

Feeding

Takes any food on offer without hesitation: flake, micro pellets, frozen bloodworm, frozen brine shrimp, frozen daphnia, live daphnia, and blanched vegetable. The natural diet in the upper layers of the water column includes zooplankton, aquatic and terrestrial insects, and seasonally worms and crustaceans, so the fish is comfortable taking food from the surface or midwater. Feeding is fast and competitive, and a bloodfin school in a community tank gets its share before slower fish reach the food. The red fin colour noticeably brightens on a diet that includes frozen or live food a few times a week; on dry flake alone the fins look duller. Two small feedings a day is enough; the activity level keeps overfeeding from being much of a risk.

Compatibility

• Faster and slightly pushier than most small tetras. In groups under six they get tense and start nipping; in groups of eight or more they leave other species alone and chase each other instead
• Not a match for long-finned species. Bettas, fancy guppies, and angelfish lose fin tissue. Short-finned, robust tankmates work much better: barbs, danios, other large tetras, corydoras, and small plecos
• Cold-tolerant for a tetra. The native range is subtropical and the species survives temperature dips into the mid-teens that would kill neons or cardinals, making it one of the few tetras suited to unheated rooms or subtropical communities with white clouds and peppered corys
• Adult cherry shrimp can be eaten and shrimplets definitely will be, despite some retailer lists calling the species shrimp-safe. Keep them out of dedicated shrimp tanks

Origin and habitat

A subtropical characin from the Rio de la Plata basin in southern central South America, with a native range across the Paraguay, Uruguay, and lower and middle Parana drainages in Argentina, Brazil, Paraguay, and Uruguay. Wild fish live in still and slow-flowing water (floodplain lakes, streams, tributaries) and prefer stretches shaded by floating or overhanging vegetation. Eigenmann and Kennedy described the species in 1903 from Asuncion, Paraguay, publishing in Proceedings of the Academy of Natural Sciences of Philadelphia. The specific epithet honours Juan Daniel Anisits (1856-1911), a Hungarian-born Paraguayan botanist who supplied the holotype to Indiana University. The genus name combines Greek aphye 'small fry' with charax 'pointed palisade stake', a reference to the densely packed sharp teeth (it is the root form used through much of the order Characiformes). The genus sits in the subfamily Aphyocharacinae, the so-called glass characins. Introduced populations exist in the Lagoa dos Patos and upper Parana in Brazil and in the Philippines; Florida specimens have been recorded but did not persist there, with the USGS identifying the fish as almost certainly an ornamental-trade escapee. Body colour is silvery with a slight blue-green sheen, set against the species' defining feature: vivid red caudal, anal, and pelvic fins, sometimes carrying through to the dorsal as well. Males are a touch slimmer, slightly more intensely coloured, and carry a small hook on the anal fin. The native range is subtropical with water temperatures between 18 and 28 C, so the fish tolerates much cooler water than the average tropical tetra and is one of the few characins that can be kept in an unheated room temperature tank in mild climates. Adult size is around 5 to 6 cm. Bloodfins are long-lived for a tetra and can exceed 10 years in well-kept aquariums. IUCN Least Concern. Often confused in the trade with the glass bloodfin tetra (Prionobrama filigera), which is from the Amazon basin and a different genus, distinguished by a more elongate, semi-transparent body and the absence of red on its anal and pelvic fins. A close relative, Aphyocharax alburnus (Goldencrown tetra), is also occasionally labelled as bloodfin in shipments. Trade specimens are almost all captive-bred.

Breeding

One of the easier characins to spawn at home. Unlike many South American tetras, bloodfins do not need soft acidic water, and a moderately hard, near-neutral setup is fine. Condition a pair on frozen food for a week, then move them into a separate breeding tank fitted with spawning mops or fine-leaved plants over a bare or mesh base, kept around 24 to 26 C. Spawning is normally triggered at dawn and often happens within a day or two. The female releases eggs that scatter through the plants while the male follows and fertilises them. Both adults will eat eggs and fry, so they need to come out as soon as spawning ends. Hatching takes around 24 to 36 hours, and the fry become free-swimming after another four or five days, during which they live off the yolk sac. First food is infusoria or a liquid fry food, with baby brine shrimp once the fry are large enough to take them. Commercial breeders run this species in outdoor ponds at scale, which is why it stays inexpensive even in larger groups.

Common problems

Among the hardier tetras in the trade. In an established tank with stable water, disease is uncommon and the species shrugs off most routine medications. Ich shows up sometimes in newly bought fish; standard heat or salt treatment works without difficulty. The most common behavioural issue is nipping when the school is too small; eight or more fish keep the activity inside the school and out of other species' fins. Bloodfins are active near the surface and will jump through any opening in the lid. A complete cover is essential. Faded fin colour is almost always a diet issue rather than a disease; adding frozen or live food restores it within a week or two. Aggression toward slower-moving tankmates (gouramis, bettas, fancy guppies) shows up as chronic stress and fin damage rather than acute attacks. Match them with species that can keep up with the pace.

Bioload

Further reading

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