Buenos Aires Tetra (Psalidodon anisitsi)

The Buenos Aires tetra is a large, fast and confident shoaling fish for an aquarium built around open swimming space. Its accepted scientific name is Psalidodon anisitsi. Many books, shops and searches still use Hyphessobrycon anisitsi, while Hemigrammus caudovittatus is an older junior synonym. These names describe the same species, but the accepted name leads this listing so the product is accurate without hiding the familiar wording people still use.

This is not a tiny, universally peaceful tetra. It is hardy and adaptable, yet its speed, appetite and occasional fin nipping make thoughtful stocking important. A group needs a long aquarium, steady filtration, open midwater, robust companions and a diet containing both animal and plant material. Tender aquarium plants may be eaten. Slow fish and long fins are poor matches.

Each size in the buy box supplies one unsexed fish per quantity selected. Selecting quantity six means six fish of that size; selecting quantity one does not supply a pair or a shoal. The two-fish gallery scene is an illustration of group behaviour, not a promise of sex, pairing or compatibility. Current price, any crossed-out saving and any shoal-price offer shown beside the live buy button are the source of truth at checkout.

Why Has the Scientific Name Changed?

The naming history is useful, not decorative. Eigenmann described the species as Hemigrammus anisitsi in 1907. It later became widely known as Hyphessobrycon anisitsi, the name still used by much aquarium literature and searched frequently in the UK. Ahl described Hemigrammus caudovittatus in 1923, but current catalogues treat that name as a junior synonym rather than a separate species.

Phylogenetic work published in 2020 resurrected and expanded the genus Psalidodon. Eschmeyer's Catalog of Fishes now records Psalidodon anisitsi as valid, and both FishBase and GBIF use that combination. The practical conclusion is simple: the current title is scientifically current, while the older names remain visible in this section and the FAQ so keepers can reconcile labels, books and search results without being sent to a duplicate product.

Origin, Habitat and Trade Provenance

Current catalogues place the species in the Parana and Uruguay river basins, across parts of Argentina, Brazil, Bolivia, Paraguay and Uruguay. Records include ponds, rivers, streams, seasonal floodwaters and connected lowland habitats. That broad subtropical distribution helps explain why the fish tolerates cooler conditions than many equatorial tetras, but it does not make the species a British coldwater fish or remove the need for stable temperature.

Wild habitat cannot be reduced to one decorative biotope. Water level, flow, food and temperature vary across a large drainage and through the seasons. In an aquarium, the most useful features are uninterrupted swimming lanes, oxygenated water, visual cover at the margins and enough footprint for the group to turn and chase without trapping weaker fish.

This listing does not claim a wild collection locality, a named river strain or a sexed bloodline. Commercial Buenos Aires tetras are commonly captive-produced, but the current stock record does not prove the breeding facility or ancestry of each fish. The correct customer promise is therefore the species and selected trade size, not an invented provenance story.

Appearance, Sexing and Buenos Aires Tetra Size

The familiar form has a silver to green-silver body, red or orange-red fins and a dark mark at the caudal peduncle. Colour changes with age, diet, lighting, background, stress and transport. Newly delivered fish can appear pale; settling into clean water with shelter and a suitable group usually reveals more contrast. The gallery images are species-reference illustrations, not photographs of the individual that will be packed.

A common aquarium adult is around 6-8 cm, and Maidenhead Aquatics gives 8 cm as a maximum in its species profile. FishBase records a much larger maximum total length of 13.2 cm. Those figures should not be collapsed into a false hard ceiling. Plan the aquarium for a robust, fast-swimming tetra and allow for exceptional size, rather than assuming every adult stops at exactly 7 cm.

Females are often deeper-bodied and more heavily built, especially when carrying eggs; males tend to be slimmer and can develop small fin hooks associated with reproduction. These differences are comparative, not a reliable promise in young retail fish. We do not select or guarantee sex, and body fullness alone must not be treated as proof that a fish is female or pregnant.

Observation	What it may mean	What it does not prove
Deep, full body	Mature female, recent feeding or individual build	Pregnancy or guaranteed sex
Slim body	Male, juvenile or lean individual	Guaranteed male
Pale colour after delivery	Transport and settling stress	Permanent adult colour
Red fins and dark tail mark	Characteristic species pattern	Exact match to an illustration

Buenos Aires Tetra Tank Size and Group Planning

Length matters more than a headline litre figure. FishBase cites an 80 cm minimum aquarium, but that is an evidence floor, not permission to crowd a vigorous group into any short 80-litre shape. For the first six, use an aquarium at least 90 cm long and roughly 100 litres. A 120 cm aquarium gives eight to ten fish substantially better swimming space and creates more options for robust tank mates.

Six is the minimum social group used for this listing. Eight or more is preferable when the aquarium can support them. A group does not guarantee perfect behaviour: it spreads attention and allows more normal interaction, but under-sized aquaria, poor feeding, weak fish or unsuitable companions can still produce chasing and nipping. Add the intended group together where possible instead of leaving one or two fish isolated for weeks.

Plan	Useful floor	Important limit
First group of six	90 cm frontage; about 100 L	Keep companions limited and robust
Group of eight to ten	120 cm frontage preferred	Increase filtration and open midwater
Mixed community	Size for the whole adult stock, not delivery size	Avoid slow or long-finned species
Breeding project	Separate dedicated aquarium	Not a reason to crowd the display tank

Always stock from adult dimensions and adult behaviour. A 3.5-4 cm fish is not a permanently small variant, and the larger size option is not a different species. Measure usable swimming length after wood, rocks and equipment are installed. A nominally large aquarium can still be cramped if decor blocks the entire middle level.

Temperature and Water Quality

The reviewed trade range is 18-27°C, with pH 6.0-7.5 and hardness up to about 18 dH. A stable 20-24°C is a sensible everyday target for a mixed indoor aquarium. The broad range describes adaptability, not a reason to swing between extremes. Match the chosen companions at the same stable point and avoid rapid changes.

Use a heater where the room cannot maintain a reliable lower limit. This species is subtropical and cool-tolerant, but it is not a licence for an outdoor pond or an unmonitored winter aquarium. At warmer temperatures, oxygen demand and metabolism rise; strong surface movement and sensible stocking become more important.

Ammonia and nitrite must remain at zero. Keep nitrate controlled through stocking, feeding, plant choice and regular partial water changes. Test source water before trying to alter pH or hardness, and use our water chemistry guide to interpret the result. Captive-produced fish usually adapt to a useful range, while sudden chemical adjustment can be more harmful than a stable value that is not numerically perfect.

Aquarium Layout, Cover and Plants

Build around a broad open swimming lane through the middle of the tank. Place wood, rounded stones and robust planting toward the back and ends so fish can leave one another's sight without losing the central run. Use a secure lid: fast characins can jump when startled, especially during transfer, maintenance or chasing.

Buenos Aires tetras have a well-established reputation for eating or damaging plants. Tender stems, fresh shoots and soft leaves are at greatest risk. Anubias, Java fern and other tough, established plants attached to hardscape may last better, but no plant is guaranteed safe. Artificial silk plants and wood can supply cover where preserving a planted display matters more than using live foliage.

The gallery scene showing fish beside a plant is not evidence that the species is plant-safe. Equally, the image labelled as a side view is not a diagnostic photograph of the exact fish supplied. The images help customers recognise the silver body, red fins and dark tail marking; the text carries the behavioural caveats that a still image cannot.

Filtration, Flow and Maintenance

Use a mature biological filter sized for the actual community and feed load. The species is an enthusiastic eater and a group creates more waste than a small nano-tetra school. Moderate circulation, clear swimming water and visible surface movement suit its active nature. Flow should not turn the entire tank into a jet or leave resting fish pinned behind decor.

Rinse mechanical media in removed aquarium water when flow falls, and avoid replacing every biological medium at once. Vacuum accessible debris, remove uneaten food and change a consistent portion of water each week according to test results. Match replacement water for temperature and dechlorinate it before contact with fish.

A mature aquarium means a functioning nitrogen cycle, not simply a tank that has held water for a set number of days. Confirm zero ammonia and nitrite before adding the group. After stocking, test more frequently while the filter adjusts to the additional load.

Shoaling Behaviour, Chasing and Fin Nipping

These tetras are active, visually bold and often first to food. Their group can look loose while browsing and tighten rapidly when startled. Short chases within the shoal can be normal, but persistent targeting, torn fins, hiding, weight loss or one fish held away from food are intervention signs.

Are Buenos Aires tetras fin nippers? They can be. Keeping six or more, supplying enough swimming room and feeding a balanced diet can reduce pressure, but none of those measures turns the species into a guaranteed peaceful companion. Long-finned fish, slow fish and very small timid tetras remain poor choices.

If trouble develops, check the whole setup before blaming one fish: group size, tank length, line-of-sight breaks, temperature, food access, sex and size imbalance, illness and crowding all affect behaviour. A backup aquarium or rehoming plan is responsible preparation for any assertive community species.

Buenos Aires Tetra Tank Mates

Choose companions that are robust, quick enough to feed and comfortable at the same temperature. Medium active characins, suitable barbs, some danios and sturdy bottom-dwellers may work in a sufficiently large aquarium. Compatibility is always conditional on adult size, individual behaviour and total stocking.

Avoid bettas, fancy guppies, long-finned angelfish and other slow fish with trailing fins. Very small shrimp may be eaten, and juvenile shrimp are especially vulnerable. Snails are usually less exposed, but no invertebrate is guaranteed safe. Large predatory fish are also unsuitable because they may eat the tetras.

For a calmer tetra display, compare the X-Ray Tetra or browse the wider tetra collection. The Bleeding Heart Tetra is another larger-bodied alternative, but it still needs its own group and a compatibility review. The Lemon Tetra suits a calmer style of aquarium and is presented as an alternative, not an automatic companion.

Companion type	Decision	Reason
Robust, active fish of similar size	Possible with space	Better able to share movement and feeding pace
Slow or long-finned fish	Avoid	Higher stress and fin-nipping risk
Tiny timid tetras	Usually avoid	Can be outcompeted or harassed
Sturdy bottom-dwellers	Often possible	Different swimming level, subject to water and footprint
Dwarf or juvenile shrimp	High risk	May be treated as food
Large predatory fish	Avoid	The tetra may become prey

Food and Feeding

FishBase records worms, crustaceans, insects and plants in the diet. In the aquarium, use a quality flake or small pellet as a dependable base, then rotate frozen or live foods such as daphnia, brine shrimp and suitable insect larvae. Include a plant-based flake, spirulina-containing food or other vegetable component rather than feeding only rich animal protein.

Feed small portions that the whole group can take within a short period. Watch the slower and smaller fish instead of judging only the first individuals at the surface. One or two modest feeds daily are usually easier to control than a large dump of food. Remove persistent leftovers and adjust the next portion.

Vegetable food may reduce pressure on plants, but it cannot guarantee that leaves will be ignored. Likewise, hunger is not the only cause of fin nipping. Diet supports condition and behaviour; it does not replace adequate group size, swimming length or compatible stocking.

Food role	Examples	Use
Daily staple	Quality flake or small omnivore pellet	Measured base diet
Animal variety	Daphnia, brine shrimp, suitable insect larvae	Rotate in modest portions
Plant component	Green flake or spirulina-containing food	Regular part of the rotation
Not appropriate	Large leftovers or one rich food every day	Raises waste and narrows nutrition

Health Checks and Quarantine

A healthy fish should swim level, respond to the group, breathe without obvious effort and show intact skin and fins. Appetite often returns quickly after transport, but do not repeatedly feed a newly delivered fish to test it. Dim light, quiet surroundings and stable water are more useful during the first hours.

Quarantine new livestock when practical. Use separate equipment, observe feeding and waste, and look for spots, excess mucus, frayed fins, clamped posture or abnormal breathing. Do not medicate the display aquarium on guesswork. Confirm water quality first and seek diagnosis before choosing a treatment, because similar symptoms can have different causes.

Hardy does not mean immune to poor conditions. Rapid temperature change, ammonia, chronic chasing and inadequate oxygen can damage this species like any other fish. Record test results and changes so a problem can be traced instead of treated as a mystery.

Arrival and Acclimation

1. Prepare a cycled, covered aquarium before delivery and test ammonia, nitrite and temperature.
2. Turn the aquarium light down and keep the unopened bag away from direct heat or sunlight.
3. Equalise temperature briefly, then follow the acclimation instructions supplied with the order or use the acclimation timer; do not extend a stressful opened-bag process unnecessarily.
4. Transfer fish without adding transport water to the aquarium where practical.
5. Keep lighting low, provide visual cover and delay feeding until the fish are settled.
6. Observe breathing, balance and group interaction closely during the first day.

Do not release one fish into an aggressive established shoal without planning. If adding to an existing group, rearranging some decor and feeding the resident fish modestly can reduce immediate focus on the newcomer, but observation and a separation plan remain essential.

Breeding Evidence and Limits

The species is oviparous and scatters eggs among plants or spawning material. Adults provide no parental care and may eat eggs. A dedicated breeding aquarium, conditioned adults, fine-leaved material or a protective mesh, and removal of adults after spawning are established elements of aquarium practice.

A controlled developmental study recorded egg and larval development at about 27°C, while FishBase notes aquarium hatching commonly within 20-24 hours. These are observations under particular conditions, not a guaranteed timetable for every home. Fertility, parent condition, temperature, water chemistry and fungal loss all affect results.

Retail juveniles are unsexed, and buying two does not create a breeding pair. A group project offers a better chance of including both sexes, but successful spawning and fry survival are never guaranteed. Keep any breeding attempt separate from the main community so eggs and fry can be managed without compromising adult welfare.

Buying a Buenos Aires Tetra for Sale in the UK

Select the available size and then choose the number of individual fish required for your planned group. The comma in a supplier-style size label is a decimal separator: for example, 3,5-4 cm means approximately 3.5-4 cm. Size bands are estimates for live animals, not exact measurements or permanent adult sizes.

The current buy box may display a lower price, crossed-out comparison price or shoal saving. Those live values can change with stock and promotions, so this description does not hard-code a future price. It also does not convert a quantity into a pair. One quantity always means one unsexed fish in the selected size option.

Livestock orders are covered by our published Live Arrival Guarantee when the order and claim meet its current terms. First-time customers can enter WELCOME10 at checkout for 10% off an eligible first order. Check the live checkout for eligibility and the final total before payment.

Is This the Right Tetra for Your Aquarium?

A good fit when...	Choose another species when...
You have at least 90 cm of swimming length	You have a nano or short aquarium
You can keep six or more together	You want one ornamental centrepiece fish
Your companions are robust and active	Your tank contains long-finned or timid fish
You accept possible plant damage	A delicate aquascape is your main priority
You want a visible, energetic midwater group	You want a quiet, slow community

If the fit is wrong, that is useful information before purchase. Explore the Glowlight Tetra listing for a smaller alternative, or browse all freshwater fish and compare adult size, group requirements and temperature before combining species.

Frequently Asked Questions

Evidence and Further Reading

This Buenos Aires tetra care guide separates accepted taxonomy, recorded biological evidence and practical aquarium recommendations. Sources were reviewed for the claims they support; differences in reported maximum size are disclosed rather than silently averaged.

• Eschmeyer's Catalog of Fishes: accepted name, synonymy and basin distribution.
• Teran, Benitez and Mirande (2020): phylogeny and resurrection of Psalidodon.
• FishBase species summary: subtropical ecology, recorded maximum length, diet, plant eating, grouping and aquarium-length evidence.
• GBIF species record: current classification and historical names.
• Maidenhead Aquatics species data bank: practical temperature, water, sexing, plant and compatibility guidance.
• Park et al. (2015): observed egg, larval and juvenile development under controlled breeding conditions.

Compare Before You Stock

Compare this energetic species with the calmer X-Ray Tetra, the larger-bodied Bleeding Heart Tetra or the smaller Lemon Tetra. These are alternatives for planning, not automatic tank-mate endorsements. Check adult size, water, group number and temperament for every species before ordering.