Bloodfin Tetra

Quick Summary

The Bloodfin Tetra is one of the hardiest and most forgiving tetras available, tolerating a wider temperature range than most tropical species and making it an excellent choice for beginners or anyone seeking a low-maintenance shoaling fish with genuine visual appeal.

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In this guide:

• Introduction
• Quick Stats
• Appearance
• Natural Habitat
• Tank Size and Setup
• Water Parameters
• Diet and Feeding
• Behaviour and Temperament
• Tank Mates

Introduction

The Bloodfin Tetra (Aphyocharax anisitsi) has been a staple of the freshwater hobby for well over a century, and for good reason. Originally described in 1903, this small South American characin combines understated elegance – a sleek silvery body offset by vivid red fins – with a constitution that borders on bulletproof. It is one of those rare species that genuinely earns the label “beginner-friendly” without being dull or unremarkable in a well-maintained aquarium.

What sets the Bloodfin Tetra apart from many of its tetra relatives is its tolerance of cooler water. While most popular tetras demand consistently tropical temperatures of 24-28 C, the Bloodfin is comfortable at temperatures as low as 18 C and will thrive in unheated indoor aquariums in many climates. This makes it an unusually versatile fish – equally at home in a standard tropical community tank or a temperate setup alongside species like White Cloud Mountain Minnows or some of the hardier corydoras.

Peaceful, active, and endlessly entertaining in a shoal, the Bloodfin Tetra is a species that rewards even minimal effort with years of reliable companionship. A well-kept group can live for five years or more, and their care requirements are straightforward enough that even a first-time fishkeeper can succeed with them from day one.

Appearance

The Bloodfin Tetra has a classic tetra silhouette – a laterally compressed, torpedo-shaped body that tapers to a forked caudal fin. The body is predominantly silvery with a faint iridescent sheen that catches the light, sometimes showing subtle olive or greenish tones along the dorsal surface depending on lighting conditions and the fish’s mood. In certain angles, a thin, faint lateral stripe may be visible running along the midline, though it is far less prominent than the bold stripes seen in species like the Neon Tetra.

The defining feature, and the source of the common name, is the vivid blood-red colouration that saturates the fins. The caudal (tail), anal, pelvic, and dorsal fins all display this striking red pigmentation, with the intensity being strongest in the anal and caudal fins. In healthy, well-conditioned specimens kept in appropriate water and offered a varied diet, the red can be remarkably intense – almost crimson – and provides a genuinely eye-catching contrast against the silver body.

Males and females are broadly similar in appearance, though there are subtle differences that become more apparent in mature fish. Males tend to be slightly slimmer and often display more vivid red colouration in the fins, particularly when in breeding condition. Females are typically a little deeper-bodied, especially when carrying eggs, and their fin colour, while still present, is usually somewhat less saturated. Some experienced keepers also report that males have a very slight hook on the anal fin, though this can be difficult to discern without close inspection.

Young Bloodfin Tetras are less colourful than adults, with the red fin pigmentation developing and intensifying as they mature. A juvenile may appear largely plain silver for the first few months of life before the characteristic finnage begins to show its full potential. This is entirely normal and not a cause for concern.

Natural Habitat

The Bloodfin Tetra originates from the Rio Parana drainage system in South America, with its range spanning parts of Argentina, Paraguay, and southern Brazil. This is a significant detail for aquarists because the Rio Parana basin encompasses a considerable range of latitudes, including subtropical and even temperate zones – explaining the species’ unusual tolerance of cooler water temperatures.

In the wild, Bloodfin Tetras inhabit a variety of freshwater environments within the basin, including slow-moving rivers, tributaries, streams, and associated floodplain habitats. They are often found in areas with moderate vegetation, submerged roots, and driftwood, which provide cover from predators and create the dappled light conditions the species seems to prefer. The substrates in these habitats are typically sandy or muddy, and the water can range from clear to moderately tannin-stained depending on the specific location and season.

Water conditions across their native range are variable, which accounts for the species’ remarkable adaptability in captivity. The pH of their natural waters can range from mildly acidic to slightly alkaline, and hardness levels vary considerably. Temperatures in the subtropical portions of the Parana basin can drop significantly during the cooler months, sometimes falling below 18 C, while summer temperatures may climb into the high twenties. This seasonal fluctuation has produced a fish that is far more temperature-tolerant than the majority of tropical tetras, which hail from equatorial regions with more stable year-round warmth.

Bloodfin Tetras are shoaling fish in the wild, forming groups that range from modest aggregations of a dozen or so individuals to much larger assemblages, depending on habitat conditions. They occupy the middle and upper water column, feeding on small invertebrates, insect larvae, and organic matter drifting in the current.

Tank Size and Setup

A group of Bloodfin Tetras requires a minimum tank size of 60 litres, which will comfortably house a shoal of six to eight individuals. However, as with all active shoaling species, a larger tank is always preferable. A 90-120 litre aquarium allows for a more natural-looking group of ten to twelve fish and gives them the swimming space they benefit from. Bloodfin Tetras are active swimmers that predominantly use the middle and upper portions of the water column, so a tank with a reasonable horizontal footprint (length and width) is more important than excessive height.

When it comes to aquascaping, the Bloodfin Tetra is not particularly demanding, but a thoughtfully arranged tank will bring out the best in the species. A combination of open swimming areas and planted zones works well. The open areas allow the shoal to swim freely and display their natural schooling behaviour, while clusters of live plants, driftwood, and other decor provide cover and visual barriers that help the fish feel secure. Suitable plant species include Vallisneria, Java Fern, Anubias, and various stem plants – none of which the Bloodfins will damage, as they are not herbivorous in any meaningful sense.

Substrate choice is largely a matter of personal preference, as the Bloodfin Tetra spends little time near the bottom of the tank. Fine gravel or sand both work perfectly well. If keeping them alongside bottom-dwelling species such as corydoras, a smooth sand substrate is the better choice for the welfare of those tank mates.

Lighting should be moderate. Bloodfin Tetras do not require intense lighting and may appear washed out or slightly nervous under very bright conditions without adequate plant cover. A moderately lit tank, or a well-lit planted tank where the vegetation provides shaded areas, will show off their silver and red colouration to best effect. The addition of some floating plants can help diffuse strong overhead lighting and create a more natural ambiance.

A secure lid or cover glass is recommended. Bloodfin Tetras are capable jumpers, particularly when startled or during the excitement of feeding. An uncovered tank poses a genuine risk of losing fish, especially in the early days after introduction when the fish are still settling in.

Water Parameters

One of the Bloodfin Tetra’s greatest strengths as an aquarium species is its broad tolerance of water chemistry. It is genuinely adaptable to a wide range of conditions, making it suitable for most tap water supplies without the need for extensive modification. That said, maintaining stable, clean water is always more important than hitting a specific number – consistency matters more than precision with this species.

The temperature range of 18-28 C is notably broader than that of most commonly kept tetras. For a general community tropical setup, a temperature of 22-25 C is a comfortable middle ground. If you are keeping Bloodfin Tetras in a cooler, subtropical-style tank, they will do perfectly well at 18-22 C – a range at which many other tetra species would struggle. This flexibility is one of the key reasons the Bloodfin Tetra is so widely recommended.

Regular partial water changes of 20-30% weekly will keep nitrate levels in check and maintain overall water quality. Bloodfin Tetras are hardier than many small fish when it comes to water quality fluctuations, but this is not an invitation to neglect maintenance. Good husbandry remains the foundation of long-term health for any aquarium species.

Filtration and Equipment

The Bloodfin Tetra does not require any specialised filtration equipment. A standard hang-on-back filter, internal filter, or canister filter rated for the aquarium’s volume will be perfectly adequate. The key requirements are effective biological filtration to process ammonia and nitrite, and sufficient mechanical filtration to keep the water clear.

Flow rate is worth considering. While Bloodfin Tetras are reasonably adaptable, they do not naturally inhabit fast-flowing rapids. A gentle to moderate flow is ideal. If using a filter with a strong output, consider using a spray bar or positioning the outlet to diffuse the current, ensuring there are calmer areas in the tank where the fish can rest without fighting the flow.

A heater is optional depending on your intended temperature range and ambient room temperature. If you are keeping the tank at standard tropical temperatures (24-26 C) or your room temperature drops below 18 C at any point during the year, a thermostatically controlled heater is a sensible investment. For keepers in warmer climates or those intentionally running a cooler subtropical setup, a heater may not be necessary – though having one available as a backup is always prudent.

Standard aquarium lighting, whether LED or fluorescent, is suitable. No UV sterilisers, protein skimmers, or other specialist equipment are needed. An air stone or similar aeration device can be beneficial, particularly in warmer weather when dissolved oxygen levels may drop, but is not strictly essential if the filter provides adequate surface agitation.

Diet and Feeding

Bloodfin Tetras are omnivorous and extremely unfussy eaters, which is another significant point in their favour for beginner fishkeepers. They will readily accept virtually any commercially available aquarium food of an appropriate size, including flake food, micro-pellets, granules, and freeze-dried products.

A good-quality flake or micro-pellet food should form the staple of their diet. Choose a product formulated for small tropical or community fish, ideally one with a balanced blend of protein, vegetable matter, and essential vitamins. Feed small amounts once or twice daily – only as much as the shoal can consume within two to three minutes. Overfeeding is a far more common problem than underfeeding and leads to poor water quality, which in turn causes health issues.

To maintain optimal health and bring out the best fin colouration, supplement the staple diet with regular offerings of protein-rich live or frozen foods. Excellent choices include bloodworm, daphnia, brine shrimp (both adult and nauplii), cyclops, and mosquito larvae. These foods more closely mirror the small invertebrates and insect larvae that Bloodfin Tetras consume in the wild, and they provide nutritional variety that a single dry food alone cannot replicate.

Frozen foods are a practical and widely available alternative to live foods, offering similar nutritional benefits without the risk of introducing parasites or diseases that can occasionally accompany live cultures from unreliable sources. Thaw frozen foods in a small amount of tank water before adding them to the aquarium.

While Bloodfin Tetras are primarily carnivorous-leaning omnivores, they will also nibble on blanched vegetable matter such as finely chopped spinach or courgette. This is not essential but can add further variety to their diet. They will also graze on any biofilm or microalgae that develops on surfaces within the tank, though they should not be relied upon for algae control.

Behaviour and Temperament

The Bloodfin Tetra is a peaceful, social species that displays classic shoaling behaviour. In the aquarium, a group will spend much of the day actively swimming together in the middle and upper water column, loosely coordinating their movements and occasionally tightening into a more cohesive school when startled or during feeding. This social behaviour is one of the species’ most appealing traits, and it is best appreciated in groups of at least six individuals, with eight to twelve or more being preferable.

Kept in insufficient numbers – fewer than six – Bloodfin Tetras may become noticeably more skittish and stressed. Solitary individuals or pairs are particularly prone to hiding, loss of colour, and reduced lifespan. The security of the group is fundamental to the species’ well-being, and this is a point that should not be compromised.

Within the shoal, there is typically a loose hierarchy, and males may engage in minor sparring – brief chases and fin displays – particularly during feeding or when vying for the attention of females. This behaviour is entirely normal and virtually never results in injury. It is a far cry from the genuine aggression seen in some other small fish species and should not be mistaken for bullying.

Bloodfin Tetras are not fin-nippers in the way that some tetra species, such as Serpae Tetras, can be. They will very rarely bother the fins of tank mates, making them suitable companions for slow-moving or long-finned species – though it is always wise to observe any new combination of fish carefully during the first few days to ensure compatibility in practice as well as in theory.

One behavioural trait worth noting is their tendency to jump. Bloodfin Tetras can and do leap from the water, particularly when startled by sudden movements, loud noises, or aggressive tank mates. As mentioned in the setup section, a secure cover is strongly recommended to prevent losses.

They are not shy feeders and will come to the surface readily at feeding time, often learning to associate the approach of their keeper with food within a few days of being introduced to a new tank. Their activity level remains fairly consistent throughout the day, though they may be slightly more active during the morning and evening.

Tank Mates

The Bloodfin Tetra’s peaceful temperament, modest size, and broad environmental tolerances make it compatible with a wide range of community species. When selecting tank mates, the main considerations are avoiding anything large or aggressive enough to predate on the Bloodfins, and ensuring that all species in the tank share compatible water parameter requirements – particularly temperature, given the Bloodfin’s unusual tolerance of cooler conditions.

Good tank mates

• Neon Tetra – A peaceful, similarly sized shoaling tetra that shares the Bloodfin’s preference for the middle water column, though best kept at the warmer end of the Bloodfin’s range.
• White Cloud Mountain Minnow – An excellent companion for cooler subtropical setups, sharing the Bloodfin’s tolerance of lower temperatures and peaceful nature.
• Bronze Corydoras – A hardy, peaceful bottom-dweller that occupies a different zone of the tank and thrives across a similar temperature range.
• Pepper Corydoras – Another robust corydoras species well suited to cooler community tanks alongside Bloodfin Tetras.
• Cherry Barb – A gentle, colourful barb that coexists peacefully with Bloodfins and adds visual contrast to the middle water column.
• Bristlenose Pleco – A peaceful algae-eating catfish that stays out of the Bloodfin’s way and is hardy enough for most community setups.
• Harlequin Rasbora – A calm, attractive shoaling species that mixes well with Bloodfin Tetras in a tropical community.
• Kuhli Loach – A peaceful, nocturnal bottom-dweller that complements the Bloodfin’s daytime activity in the upper water column.
• Amano Shrimp – Large enough to avoid being eaten by Bloodfins and an excellent addition for algae control in a planted tank.

Fish to avoid

• Oscar – Far too large and predatory; would readily consume Bloodfin Tetras.
• Convict Cichlid – Aggressive and territorial, especially when breeding, and poses a serious threat to small tetras.
• Red Tail Catfish – A massive predatory catfish entirely unsuitable for community tanks with small fish.
• Serpae Tetra – While superficially similar, Serpae Tetras are notorious fin-nippers that can harass Bloodfins and other peaceful species.
• Tiger Barb – Known for fin-nipping behaviour that can stress and injure Bloodfin Tetras, particularly if the barb group is too small.
• Jack Dempsey – A large, aggressive cichlid that would view Bloodfin Tetras as food.
• Green Terror – Highly aggressive and far too large to coexist safely with small tetras.

Breeding

Breeding Bloodfin Tetras is achievable for hobbyists with a modest amount of preparation, though raising the fry to adulthood requires more attention than the general care of the adults. The species is an egg-scatterer, showing no parental care whatsoever – in fact, the adults will readily consume their own eggs and fry if given the opportunity.

To encourage spawning, begin by conditioning a group of healthy adults with frequent feedings of high-quality live or frozen foods such as brine shrimp, daphnia, and bloodworm for one to two weeks. This protein-rich diet helps females develop eggs and brings both sexes into breeding condition. Females carrying eggs will appear noticeably rounder when viewed from above or from the front.

A separate breeding tank is strongly recommended. A small tank of 20-30 litres is sufficient. Fill it with water from the main tank or prepare water that is slightly softer and more acidic than usual (pH around 6.5, GH 4-8 dGH), at a temperature of 24-26 C. The bottom of the tank should be covered with a spawning mop, a layer of fine-leaved plants such as Java Moss, or a mesh grid that allows eggs to fall through but prevents the adults from reaching them. Lighting should be dim.

Introduce a well-conditioned pair or a small group (two males to one female, or a similar ratio) into the breeding tank in the evening. Spawning typically occurs the following morning, often triggered by the first light of day. The female scatters adhesive eggs among the plants or spawning medium while the male fertilises them. A single spawning can produce several hundred eggs, though smaller clutches of 50-150 are more common, especially from younger females.

Remove the adults immediately after spawning is complete, as they will begin eating the eggs without hesitation. The eggs are small and semi-transparent, hatching in approximately 24-36 hours at 25 C. The resulting fry are tiny and will absorb their yolk sacs over the next two to three days before becoming free-swimming.

Once free-swimming, the fry require very small food. Infusoria or commercially available liquid fry food is suitable for the first few days, after which they can graduate to freshly hatched brine shrimp nauplii and microworms. Feed small amounts several times daily, and keep the water impeccably clean with gentle sponge filtration and small, frequent water changes. Growth is reasonably steady, and the young fish will begin to show their characteristic red finnage at a few months of age.

Common Diseases

Bloodfin Tetras are among the hardier species in the hobby and are not especially prone to any species-specific diseases. However, like all aquarium fish, they are susceptible to the common ailments that can affect freshwater species when water quality deteriorates or when stress compromises their immune systems.

Ich (White Spot Disease) is perhaps the most frequently encountered illness in community aquariums. It presents as small white cysts resembling grains of salt on the body and fins. Bloodfin Tetras can contract ich, particularly after the stress of transport or introduction to a new tank, or when water temperatures fluctuate sharply. Treatment involves gradually raising the water temperature to 28-30 C (within the species’ tolerance) and, if necessary, using a proprietary ich medication. Ensure any medication used is safe for tetras, as some treatments containing copper or formalin can be harsh on small characins at full dosage.

Fin rot is another condition that may occasionally be seen, typically as a result of poor water quality or physical damage to the fins. It manifests as fraying, discolouration, or erosion of the fin edges. Improving water quality through more frequent water changes is often sufficient to halt and reverse mild cases. More advanced fin rot may require treatment with an antibacterial medication.

Columnaris (sometimes mistaken for a fungal infection) can present as white or greyish patches on the body, mouth, or fins. It is a bacterial infection that thrives in warm water and is often associated with stress or overcrowding. Treatment typically involves antibacterial medications and addressing the underlying cause of stress.

Internal parasites can occasionally affect Bloodfin Tetras, particularly wild-caught or poorly quarantined specimens. Symptoms may include weight loss despite normal feeding, white stringy faeces, or a generally emaciated appearance. Anti-parasitic foods or medications can be used to treat these issues.

The single most effective disease prevention strategy is maintaining excellent water quality through regular partial water changes, avoiding overstocking, feeding a varied and nutritious diet, and quarantining new fish for at least two weeks before adding them to an established community. A well-maintained Bloodfin Tetra is a remarkably robust and long-lived fish that rarely presents health problems.

FAQs

Can Bloodfin Tetras live in an unheated tank?

Yes, provided the room temperature does not regularly fall below 18 C. Bloodfin Tetras are one of the few commonly available tetras that genuinely thrive at cooler subtropical temperatures. In many homes, an indoor aquarium will remain within an acceptable range year-round without a heater. However, if your home gets particularly cold in winter, a heater set to a low temperature (around 20 C) provides a useful safety net.

How many Bloodfin Tetras should I keep together?

A minimum of six is recommended, but eight to twelve or more is preferable. Bloodfin Tetras are social shoaling fish that display more natural, confident behaviour and show better colouration when kept in larger groups. A solitary Bloodfin Tetra or a pair will be stressed, skittish, and far less enjoyable to observe than a proper shoal.

Do Bloodfin Tetras nip fins?

Bloodfin Tetras are not considered fin-nippers under normal circumstances. They are significantly less nippy than some of their tetra relatives, such as Serpae Tetras or Buenos Aires Tetras. While no guarantee can be made about individual fish behaviour, fin-nipping is very rarely reported with this species, and they are generally safe to keep with slow-moving or long-finned tank mates.

Why are my Bloodfin Tetras losing their red colour?

Colour loss in Bloodfin Tetras is most commonly caused by stress, poor water quality, an inadequate diet, or keeping the fish in too small a group. Ensure you are maintaining clean water with regular water changes, feeding a varied diet that includes protein-rich frozen or live foods, and keeping a proper shoal of at least six fish. Dim or overly harsh lighting can also make the red colouration appear less vivid. If water parameters and husbandry are correct, the colour should improve over a few weeks.

Are Bloodfin Tetras suitable for a planted tank?

Absolutely. Bloodfin Tetras are entirely plant-safe and will not damage or uproot live plants. They actually look their best in a well-planted aquarium where the green foliage provides a contrasting backdrop to their silver bodies and red fins. Plants also offer the cover and visual barriers that help the fish feel secure, promoting bolder behaviour and better colouration.

Related Guides

• Buenos Aires Tetra – Another hardy South American tetra with excellent cool-water tolerance, though more boisterous and less plant-safe than the Bloodfin.
• White Cloud Mountain Minnow – A popular subtropical companion species that pairs beautifully with Bloodfin Tetras in cooler community setups.
• Ember Tetra – A smaller, warm-water tetra for keepers who enjoy the tetra family and want to explore other species with vivid colouration.
• Bronze Corydoras – A versatile, temperature-tolerant bottom-dweller that makes an ideal tank mate for Bloodfin Tetras across their full temperature range.
• Cardinal Tetra – A classic tropical tetra for comparison, showcasing different care requirements and the diversity within the characin family.