Buenos Aires Tetra Care Guide

The Buenos Aires tetra is a hardy, handsome, cool-water tetra and a dual hazard to the planted peaceful community most people picture: it is both a confirmed fin-nipper of long-finned, slow fish and a voracious plant-shredder that strips soft live plants bare. It is genuinely easy to keep alive — one of the toughest aquarium fish there is — but a classic beginner stocking trap. Keep it only in a long tank, in a big group, with tough plants or none, and robust, fast, similarly boisterous tankmates.

Buenos Aires Tetra at a glance

The sourced figures the welfare engine uses to judge Buenos Aires Tetra — the parseable key facts.

Where it comes from

This is a fish of the temperate-leaning south, not the warm tropics. It is widespread in the Río de la Plata basin — the Paraná and Uruguay river systems across Argentina, Paraguay, Uruguay and south-eastern Brazil — in vegetated still-to-slow waters, ponds, ditches and river margins. FishBase classifies it as subtropical, and that one fact drives the care: a temperate origin is why it tolerates cool, unheated water; a weedy habitat where it grazes vegetation is why it has such a destructive herbivorous streak in aquaria; and a robust, fluctuating wild environment is why FishBase calls it "one of the hardiest tropical fishes for the home aquarium", forgiving of a wide pH, hardness and temperature band.

Did you know?

• It is a genuinely cool-water tetra. Classified subtropical by FishBase, it thrives in unheated, room-temperature tanks down to about 18 °C / 64 °F — unusual among the tropical-by-default tetras and a real point of difference.
• It is the plant-destroyer of the tetra world. The herbivory is strong enough that keepers sometimes use it as a grazer, yet it will strip a planted tank bare — "they will destroy every live plant in your tank".
• It is one of the largest commonly sold tetras — a wild maximum of 13.2 cm total length, and around 6–8 cm in the tank, far bigger than the neon it gets shelved beside.
• Its name has wandered: from Hemigrammus to Hyphessobrycon to, since a 2020 revision, Psalidodon, and it still carries the old synonym Hemigrammus caudovittatus seen in older books.
• Plant-eating intensity is genuinely contested at the individual level — some keepers report big schools leaving plants untouched while others see them chomp regardless of feeding — but the risk that it will wreck soft plants is well-established, so plan for the destructive case.
• IUCN Least Concern, assessed in March 2021 — abundant and widespread.

Tank size — and why

Treat a standard 30 US gallon, roughly 90 cm-long tank as the practical floor, and beware "30 gallon" tanks that are tall and short rather than long — the database sources call for 80–100 cm of length. The driver is a large (~7 cm in the tank, up to ~13 cm in the wild), fast, boisterous, active mid-water swimmer kept in numbers: it needs swimming length and the group size that diffuses its aggression, plus a moderate bioload from a big, hungry omnivore. Prioritise footprint over height for the high-energy swimming lane, and fit a lid, as these are powerful swimmers. Twenty gallons, which some blogs allow, is too small for a proper shoal.

As a guide, a 30-gallon tank comfortably suits about 8–12 Buenos Aires Tetra as a single-species display, leaving room for tankmates.

How big does it really get?

Full-grown Buenos Aires Tetra reach about 7 cm (2.8 in) long, but they are usually sold at only about 2.5 cm (1 in) — a typical shop size (estimate). At full size, Buenos Aires Tetra needs roughly a 30-gallon tank, about 76 cm long; a common 10-gallon starter kit is only about 51 cm.

Adult size is sourced; the shop size is a typical-juvenile estimate; tank length is approximate for a standard 30-gallon aquarium.

Water parameters in practice

Cool tolerance is the headline and a genuine selling point. Aim for about 22–24 °C for a community, but the fish is comfortable from roughly 18 to 28 °C (64–82 °F) and genuinely suits unheated, room-temperature and subtropical setups — pairing better with temperate fish like white cloud minnows or hillstream loaches than with warm soft-water tetras or discus. On chemistry it is the opposite of the fragile cardinal: wild fish sit around pH 6.5–7.5 and GH 4–12, but it tolerates a very wide band (roughly pH 5.8–8.5, hardness to ~20 dGH), so it is hard-water- and tap-water-friendly. The risk with this species is behavioural, not chemical — it is almost too easy to keep alive.

Diet & feeding

An omnivore with a strong plant component — FishBase lists worms, crustaceans, insects and plants. That herbivorous streak is the defining husbandry problem: it is a voracious grazer that destroys soft aquarium plants. AquariumStoreDepot puts it bluntly — "they will destroy every live plant in your tank" — with soft species such as Vallisneria, Amazon sword and Cabomba stripped within days or weeks, while tougher Java fern and Anubias mostly survive. It is otherwise a non-fussy, greedy eater of flake, pellet, frozen, freeze-dried and live foods. Feed about two small meals a day, and deliberately include vegetable matter (spirulina or veggie wafers, blanched spinach or courgette) to satisfy the herbivory — this reduces, but does not eliminate, the plant-grazing. One important link: underfeeding directly increases fin-nipping, so a well-fed, well-vegetabled fish is a calmer one.

Gear & setup

A heater is optional given the cool tolerance — this fish is at home in an unheated room-temperature tank — but a filter handling moderate flow suits this robust, oxygen-loving swimmer. The aquascape is where it bites back: only tough plants survive, so build with Java fern, Anubias, hardscape (rock and wood) or go deliberately plant-free, and don't waste money on a soft-leaved "showcase" planting. Substrate is not fussy. Fit a lid for these active, powerful swimmers.

Temperament & behaviour

A boisterous, semi-aggressive shoaling fish — "boisterous shoaler, can be nippy" sums it up. It is not a predator, but it is a persistent fin-nipper and bully toward calmer, long-finned and slow fish, worst when underfed or under-grouped. The single most important behavioural fact is that group size is an aggression-management tool: a large group in a long tank, well-fed with vegetable matter, keeps the aggression mostly intramural; a small group in a small tank, underfed, sees fins shredded right across the community. Aggression is reported to decrease markedly once the school passes about five fish.

Group & social needs

A shoaling fish that must be kept in numbers, and here the group size is the primary welfare lever rather than a cosmetic preference. Six is a bare minimum; eight to ten or more is the real target, with some keepers running ten to twelve. Bigger schools direct the energy among themselves instead of at tankmates. Frame the group size explicitly as the way you manage this fish's aggression — under-stock it and it turns its boisterousness on whatever else is in the tank.

Compatible tank mates (preview)

A short, engine-cleared shortlist — the species TankStocking's welfare engine clears with Buenos Aires Tetra and that suit its size and temperament best. Tap any to load the pairing in the planner.

• Black Neon Tetra — Peaceful temperament, similar adult size.
• Black Phantom Tetra — Peaceful temperament, similar adult size.
• Boesemani Rainbowfish — Peaceful temperament, similar adult size.

This engine-cleared shortlist is Buenos Aires Tetra's tankmate surface for now — a dedicated tank-mates guide can follow for high-demand species.

Breeding & sexing

Sexing is moderately easy in mature fish: males are slimmer and more intensely coloured, with brighter red, orange or yellowish fins, while females are deeper-bodied and rounder, plumper when gravid. Breeding is easy by tetra standards in a dedicated setup — a willing, prolific egg-scatterer (one source rating it difficult is the outlier). Use a separate spawning tank with fine-leaved plants or spawning mops, condition the group on live foods, and trigger with slightly soft, slightly acidic water and a small temperature or water-change cue. It shows no parental care and is cannibalistic, so remove the adults immediately. Egg counts are genuinely source-dependent — quoted anywhere from several hundred to around 2,000 — and eggs hatch in roughly 20–24 hours, with fry free-swimming within a few days; start them on infusoria-grade foods, then microworm and baby brine shrimp.

Lifespan

About five years with good care, and well-kept fish reach six to seven; one source is more conservative at three to five. Given the hardiness, it is far more likely to be rehomed for its behaviour than to die young. What shortens it is chronic stress from too small a group or a cramped tank, and — less often, because it is so tough — poor water quality.

Common mistakes

• Buying it as a "peaceful community tetra". It is semi-aggressive and a fin-nipper — the single biggest conceptual error.
• Putting it in a planted showcase tank. It will shred soft plants — "they will destroy every live plant in your tank" — so use Java fern, Anubias and hardscape, or go plant-free.
• Mixing with long-finned, slow or tiny fish. Bettas, angelfish, fancy guppies, fancy gouramis, fancy goldfish, neon and ember tetras, and shrimp are nipped, out-competed, harassed or eaten, which is why those long-finned/slow species are kept off this fish's recommended tankmate list regardless of a coarse size match.
• Too small a group or too small a tank. Under six (ideally under eight to ten) in a short tank and aggression spikes onto tankmates; buy eight to ten or more in a 90 cm / 30 gallon-plus long tank.
• Underfeeding. A hungry Buenos Aires tetra nips more; feed adequately and include vegetable matter to take the edge off both the hunger and the plant-grazing.

Signs of trouble

• Nipped, frayed fins on its tankmates — the first and clearest sign the group is too small, the fish is underfed, or the tankmates are the wrong (long-finned, slow) sort; the secondary fin rot usually lands on the victims.
• Soft plants suddenly ragged or stripped — normal grazing for this fish, and a signal to switch to tough plants or add vegetable food.
• Rising aggression, loss of colour, clamped fins or lethargy in the tetras themselves — usually an under-grouped school or a cramped tank.
• White spots with flashing or scratching — ich, uncommon in this robust fish and generally stress- or chill-driven.

Is this fish right for you?

Don't buy Buenos Aires tetras if you want a peaceful planted community, if you keep or want bettas, angelfish, fancy guppies, shrimp or small shy fish, if you can't provide a long ~90 cm / 30 gallon-plus tank, or if you can't keep a group of eight to ten. There are no prominent dyed or balloon-morph welfare issues here — an albino strain is sold and is benign — so the real welfare problem is mis-stocking: a cheap, hardy fish sold to beginners who put it in exactly the wrong peaceful, planted, long-finned tank.

Bringing one home

Acclimate gently as for any tetra — float to match temperature, then add tank water over about twenty minutes — but this hardy, adaptable fish handles the move better than most, and a stable cycled tank matters more than fussing over exact parameters. Quarantine new stock as a matter of routine. Worth doing before they arrive: get the group size, the long tank, the tough-or-no plants and the robust tankmates right first, because the welfare risk here is the stocking decision, not the acclimation.

Common questions

Are Buenos Aires tetras aggressive or fin-nippers?

Yes — they are semi-aggressive and confirmed fin-nippers of long-finned, slow fish, worst when underfed or kept in too small a group. The cure is a big group (eight to ten or more) in a long tank, fed well with vegetable matter, alongside robust fast tankmates only. Aggression drops noticeably once the school passes about five fish.

Do Buenos Aires tetras eat live plants?

Yes, voraciously. They strip soft species like Vallisneria, Amazon sword and Cabomba within days or weeks, while tough Java fern and Anubias usually survive. Plant with Java fern, Anubias and hardscape or go plant-free, and feed vegetable matter to reduce — not eliminate — the grazing.

Can Buenos Aires tetras live in an unheated or cold-water tank?

Largely yes. They are subtropical and comfortable from about 18 to 28 °C (64–82 °F), so they suit unheated room-temperature and subtropical community tanks — a real advantage over warm-water tetras. Aim for around 22–24 °C in a community.

What tank size and group do Buenos Aires tetras need?

A long ~90 cm / 30 US gallon tank as the floor (prioritise length over gallons), with a group of eight to ten or more; six is a bare minimum. The space and group size exist mainly to diffuse the fish's aggression, not just for swimming room.

What fish can live with Buenos Aires tetras?

Robust, fast, similarly-sized or larger fish that can't be caught or out-competed — larger tetras, barbs (tiger, rosy), giant danios, rainbowfish, and sturdy bottom-dwellers like Corydoras and bristlenose plecos. Avoid bettas, angelfish, fancy guppies, fancy gouramis, fancy goldfish, tiny shy fish and shrimp.

Are Buenos Aires tetras hardy and good for beginners?

They are exceptionally hardy and easy to keep alive — FishBase calls them one of the hardiest aquarium fish — but they are a beginner stocking trap, because the obvious peaceful, planted, long-finned community is exactly the wrong one for them.

Sources & confidence

Sources & confidence (9 species)

These back the Buenos Aires Tetra figures and the previewed tank mates above. Each figure is read from the TankStocking species database (v2026.06); below is the care reference behind it and how confident we are in that data. Confidence reflects the source quality, not whether any pairing is safe. Full source list and the welfare model are on the methodology page.

• Buenos Aires Tetra Hyphessobrycon anisitsi — Aquadiction / Fish Laboratory (Hyphessobrycon/Psalidodon anisitsi) high confidence
• Black Neon Tetra Hyphessobrycon herbertaxelrodi — Seriously Fish / Aqua-Fish (Hyphessobrycon herbertaxelrodi) high confidence
• Black Phantom Tetra Hyphessobrycon megalopterus — Seriously Fish (Hyphessobrycon megalopterus) high confidence
• Boesemani Rainbowfish Melanotaenia boesemani — Seriously Fish; Aquarium Co-Op Boesemani guide high confidence
• Bolivian Ram Mikrogeophagus altispinosus — Seriously Fish (seriouslyfish.com/species/mikrogeophagus-altispinosus) high confidence
• Brilliant Rasbora Rasbora einthovenii — Seriously Fish (seriouslyfish.com/species/rasbora-einthovenii) high confidence
• Bristlenose Pleco Ancistrus sp. — Aquarium Source / aqua-fish.net Ancistrus care guides high confidence
• Bronze Corydoras Corydoras aeneus — Seriously Fish (seriouslyfish.com/species/corydoras-aeneus) high confidence
• Checker Barb Oliotius oligolepis — Seriously Fish — Oliotius oligolepis (https://www.seriouslyfish.com/species/oliotius-oligolepis/) high confidence

Care-guide sources (8)

This guide synthesises the references below; where they disagree, the range and the disagreement are noted in the text above. The figures in the key-facts box are read from the TankStocking species database (v2026.06). Full welfare model on the methodology page.

• FishBase — Psalidodon anisitsi — valid name Psalidodon anisitsi (Eigenmann 1907), family Acestrorhamphidae, max 13.2 cm TL, Paraná/Uruguay basin range, subtropical climate, omnivore diet ("worms, crustaceans, insects and plants")/trophic level 3.0, IUCN Least Concern (2021), "eats plants; groups of 5+; minimum 80 cm" and "one of the hardiest tropical fishes for the home aquarium"
• AquaInfo — Psalidodon anisitsi / Buenos Aires Tetra — Eigenmann 1907, synonyms, Argentina/Brazil/Paraguay range, wild pH 6.5–7.5 / temp 18–24 °C / GH 4–12, wild to 13 cm / aquarium 5–8 cm, min 100 cm for 6, "semi-aggressive" + nips fins esp. underfed, plant-nibbler, omnivore, sexing, egg-scatterer ~600 eggs hatch ~24 h, cannibalistic
• Wikipedia — Buenos Aires tetra — Psalidodon anisitsi (Eigenmann 1907), original Hemigrammus anisitsi, Acestrorhamphidae, synonyms, Río de la Plata basin, type locality Villarrica Paraguay, max ~7.5 cm, plant-nipping, fin-nipping when underfed, aggression decreases in schools of 5+, scatter-spawning eggs hatch ~24 h, red-tipped fins + black caudal cross-mark
• aqua-fish.net — Buenos Aires Tetra Care — size 5–6 cm, lifespan 5–7 yr, temp 20–26 °C ideal / tolerates 18–28 °C, pH 6.0–7.5, GH 2–12, "long tank of 80–90 cm minimum for a shoal", group 8–10, "boisterous shoaler—can be nippy", plant-nipper, omnivore, sexing, egg-scatterer hatch ~20–24 h
• AquariumStoreDepot — Buenos Aires Tetra Care Guide — size ~7 cm, lifespan 5–7 yr, temp 64–82 °F / "tolerates unheated tanks down to 64 °F", pH 6.0–7.5, GH 2–20, 30 gal for 8+, school 8 (10–12 rec), "semi-aggressive fin nippers", "they will destroy every live plant in your tank" (Java fern/Anubias survive), veg supplementation, sexing, up to ~2,000 eggs, good/bad tankmate lists
• Fish Laboratory — Buenos Aires Tetra Ultimate Care Guide — size ~3 in, lifespan ~6 yr, temp 64–82 °F, pH 5.8–8.5, min 25–30 gal, school 6+, "they will nip the fins of long finned, slow moving fish", "they will eat live plants" regardless of species, omnivore, sexing, egg-scatterers that eat fry, good/bad tankmate lists
• Aquarium Co-Op Forum — Buenos Aires tetra threads — hobby-consensus corroboration: voracious eaters; contested plant-eating (some keepers report schools of 12–25 leaving plants untouched, others report chomping regardless of feeding); keep schools of 6+ to redirect aggression among themselves
• Fishkeeping World — Buenos Aires Tetra Care Guide — ~3 in, lifespan ~3–5 yr (conservative), 20 gal "best", group 5+, fin-nipping as "learned behavior" worst when underfed, dislikes hard water/high nitrate-phosphate, avoid long-finned and much larger fish

More on Buenos Aires Tetra

Related guides on TankStocking — each scored by the same welfare engine as the planner.

This care guide is a sourced planning reference, not veterinary advice — individual fish, filtration and maintenance all matter. Cycle the tank, test your water, and observe your fish. How TankStocking works →