Black Phantom Tetra Care Guide

The black phantom tetra is a hardy, genuinely peaceful nano-tetra whose single best feature is a behaviour you only see if you stock it correctly: mature males "mock-fight," flaring their oversized black fins flank-to-flank in harmless boxing-match displays. Buy a lone fish or a same-sex trio, or drop it into a bright bare tank, and you get a drab, shy fish that looks nothing like the photos and may even start nipping.

Black Phantom Tetra at a glance

The sourced figures the welfare engine uses to judge Black Phantom Tetra — the parseable key facts.

Where it comes from

It comes from the still and sluggish waters of the upper Madeira and upper Paraguay basins in Bolivia and Brazil — floodplain backwaters, ponds, small lakes and the seasonally inundated Pantanal wetlands, among marginal vegetation, submerged roots and fallen branches. That biotope explains the care. The slow, vegetated, shaded origin is why it wants gentle flow rather than current, plenty of plants and subdued light to bring out its smoky colour and confidence; a bright bare tank washes it out. And because its wild water runs soft-to-moderate and only slightly acidic (roughly pH 5.0–7.0) rather than the extreme blackwater of a cardinal, it is far more adaptable and tolerant of ordinary community water — which is exactly why it earns its reputation as a good beginner tetra.

Did you know?

• Its name is a fin reference: megalopterus literally means "large-finned," and Eigenmann named it in 1915 for the male's outsized fins — the very stage for its mock-fighting display.
• The mock-fight is its hero feature — a "slow-motion boxing match" of constant, harmless fin-flaring duels, among the most watchable behaviours of any nano-tetra and entirely damage-free in a proper group.
• You can sex it at a glance: black fins = male, red/pink fins = female, making it a favourite "learn to sex your fish" species.
• There is a wild red form: at the popularised northern collection sites the smoky-black morph dominates, but a naturally reddish morph is reported from the southern Pantanal, blurring the line with its cousin the red phantom (a single-source field report, treat as unconfirmed).
• A taxonomic comeback: its original 1915 genus Megalamphodus was revalidated in 2024 and now anchors its own subfamily, Megalamphodinae — a live example of fish taxonomy in motion.

Tank size — and why

A 20 US gallon footprint (around 80 cm long, ~75 L) is the sound practical floor for a proper mixed-sex group; 15 gallons is a tight minimum for six. The driver is not bioload — this is a small, low-waste fish — but swimming lane, group size and, critically, horizontal room for the males to display and spar without crowding into real aggression. A longer tank gives better displays and a calmer, more colourful group, so prioritise footprint over height: the sparring and schooling happen along a horizontal lane.

As a guide, a 20-gallon tank comfortably suits about 8–12 Black Phantom Tetra as a single-species display, leaving room for tankmates.

See it to scale

Adult Black Phantom Tetra reach only about 3.6 cm (1.4 in) long — close to the size they are sold at, so what you see is roughly what you get. The catch is the group: a proper shoal still needs about a 20-gallon tank, around 76 cm long.

Adult size is sourced; tank length is approximate for a standard 20-gallon aquarium.

Water parameters in practice

Aim for a mid-70s Fahrenheit community setting, around 23–26 °C, with the fish comfortable anywhere across 20–28 °C. It prefers the soft-to-neutral, slightly acidic end (pH roughly 6.0–7.0, tolerating 5.0–7.5) and soft-to-moderately-hard water, about 2–12 dGH. Beyond the chart, this is one of the more forgiving tetras — it shrugs off normal swings far better than a cardinal — but "hardy" is not "bombproof": it still needs a cycled, stable, low-nitrate tank. The breeding water is more demanding and more acidic than the day-to-day range.

Will it thrive in your water?

The comfortable range for Black Phantom Tetra is about 20–28 °C (68–82 °F) and pH 5–7. Test your own tap water against it below.

These are the sourced comfortable ranges. Stable water matters more than chasing an exact number — a steady reading inside the band beats a "perfect" one that drifts. Some fish also need a particular water hardness (GH); where that applies, the prose above covers it.

Diet & feeding

An omnivorous micro-predator. In the wild it takes small invertebrates, crustaceans and filamentous algae foraged among roots and vegetation. In the tank, build the diet on a good-quality micro flake, crushed flake or nano pellet, and vary it with small live or frozen foods — bloodworm, mosquito larvae, daphnia, moina, cyclops, baby brine shrimp and microworm — which deepen colour and condition fish for breeding. Feed small amounts once or twice a day, only what they finish in a couple of minutes, since overfeeding fouls the water faster than it nourishes the fish. They are active mid-water feeders that dart up readily once settled.

Gear & setup

A heater to hold the warm setpoint, a gentle filter delivering soft flow (this is a still-water floodplain fish, not a current lover), and a planted, shaded layout. Dark substrate markedly intensifies colour and reduces stress — light substrate visibly washes them out — so pair it with fine-leaved plants, driftwood, some floating cover and open swimming lanes that mimic the vegetated floodplain. Keep the tank covered; there is a small but real jump risk for an active tetra.

Temperament & behaviour

Peaceful and loosely-shoaling by default, and the headline behaviour is the male display. Mature males face off flank-to-flank, spread their tall black dorsal, anal and pelvic fins and posture at one another — a slow-motion boxing match that provides constant entertainment without any physical contact or damage in a properly stocked tank. This is dominance theatre, not combat, and it is the whole reason to keep several males. The display is female-triggered and number-dependent: it is most frequent and intense when both sexes are present and several males are competing. The important caveat is that understocked or stressed fish can turn nippy and may pick at long-finned slow tankmates — the fix is numbers, not removal.

Group & social needs

Keep a real group. Six is the bare minimum; eight to ten or more, mixed-sex with at least two or three males, is the real target. The signature sparring only appears with several males and females present, so treat group size and sex mix as the single most important husbandry lever for this species. Understocked fish stay drab, shy and twitchy; a big mixed-sex group in a planted, dim, long tank gives confident, colourful fish with near-constant male display.

Compatible tank mates (preview)

A short, engine-cleared shortlist — the species TankStocking's welfare engine clears with Black Phantom Tetra and that suit its size and temperament best. Tap a name for its care guide, or use + to load the pairing in the planner.

• Amano Shrimp+Peaceful temperament, similar adult size
• Assassin Snail+Uses the bottom zone, peaceful temperament, similar adult size
• Black Neon Tetra+Peaceful temperament, similar adult size
• Bronze Corydoras+Uses the bottom zone, peaceful temperament, similar adult size
• Cardinal Tetra+Peaceful temperament, similar adult size
• Celestial Pearl Danio+Peaceful temperament, similar adult size
• Checker Barb+Peaceful temperament, similar adult size
• Cherry Barb+Peaceful temperament, similar adult size

A note on the shrimp and snails here: Black Phantom Tetra is peaceful and generally invertebrate-safe — but almost any fish will take very small shrimplets given the chance, so give shrimp dense cover (moss, leaf litter) if you want a colony to grow, rather than expecting every baby to survive.

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

Breeding & sexing

Sexing is unusually clear for a tetra: black fins mean male — a tall, pointed, sail-like dorsal and enlarged black pelvic and anal fins on a slimmer, smoky-grey body — while red or pink fins mean female, with a deeper, rounder body and reddish pelvic, anal and adipose fins. Breeding is rated moderate, easier than the cardinal, and the fish spawns readily once well-conditioned. Use a separate, dimly-lit spawning tank with soft, slightly acidic water (around pH 5.5–6.5) at roughly 24–27 °C, with fine-leaved plants, a spawning mop or a mesh/marble layer to protect the eggs from the egg-eating parents. The natural trigger is the wet-season flood, simulated by a soft-water change at daybreak. Remove the adults after spawning; eggs hatch in about 24–36 hours and fry are free-swimming a few days later, started on infusoria or liquid fry food, then microworm and baby brine shrimp.

Lifespan

Three to five years in a well-maintained tank. What shortens it is chronic stress from too small a group or a bare, brightly-lit tank, poor water quality and high nitrate, transport stress in fresh imports, and aggressive or fin-nipping tankmates.

Common mistakes

• Keeping too few, or males without females. Under six, or a same-sex group, you get no display behaviour, drab colour and a shy or even nippy fish — buy 8–10 mixed-sex with several males. This is the number-one mistake for the species.
• A bright, bare, light-substrate tank. It washes the colour out completely; true colour only emerges over weeks in a dark, planted, shaded setup.
• Expecting instant colour. Store specimens look grey and stressed — don't reject the species on its tank-of-origin look; give it weeks in a proper tank.
• Pairing it with long-finned, slow tankmates such as bettas or fancy guppies, which risks fin-nipping, especially if the group is too small.
• Confusing it with the black widow / black skirt tetra — a larger, two-barred, genuinely nippy fish — or buying it expecting red-phantom red. Know which phantom you want.

Signs of trouble

• Colour fading to pale grey and a fish hanging apart from the group — usually too small a group, a bright bare tank, or water quality.
• Clamped fins, hiding and loss of appetite — general stress cues worth investigating early.
• Twitchy or erratic swimming — often social stress from being understocked rather than illness.
• Curved spine, body lumps or a spreading whitish patch under the skin — possible neon tetra disease, the microsporidian that afflicts characins; isolate the fish.

Is this fish right for you?

Don't buy black phantoms if you can't house a group of at least six (ideally 8–10 mixed-sex), if you only want one or two "centrepieces," if your tank is bright and bare with no plants, or if your community is built around delicate long-finned slow fish or large cichlids and big-mouthed predators their size. On stock quality the news is good: no dyed or balloon morphs are common for this species, and most trade fish are commercially captive-bred and hardy — just choose active fish with intact fins and no white patches or spinal curves.

Bringing one home

It is hardy but still benefits from care on arrival: float the bag to match temperature, then add tank water gradually over fifteen to twenty minutes before netting the fish across into a mature, cycled, soft-neutral tank and leaving the transport water behind. Quarantine new stock, as fresh imports are most fragile in the first weeks, and expect true colour to develop over the following weeks rather than on day one.

Common questions

Do black phantom tetras fight?

Males "mock-fight" — they face off flank-to-flank, flare their tall black fins and posture in a slow-motion boxing match, but there is no physical contact and no damage in a properly stocked tank. It is display, not combat, and it is the reason to keep several males alongside females.

How many black phantom tetras should I keep?

Six is the bare minimum; 8–10 or more, mixed-sex with two or three males, is the real target. The signature male display only appears with several males and females present, and understocked fish stay drab, shy and occasionally nippy.

Are black phantom tetras hardy or good for beginners?

Yes — they are among the more forgiving tetras, hardier than the red phantom or cardinal, and tolerant of ordinary community water across roughly pH 6–7 and 23–26 °C. They still need a cycled, stable tank; hardy is not bombproof.

How do you tell male from female black phantom tetras?

By fin colour. Males have all-black fins, including a tall, pointed, sail-like dorsal and enlarged black pelvic and anal fins, on a slimmer smoky-grey body. Females are deeper and rounder with shorter fins tinted reddish or pink.

What's the difference between a black phantom and a red phantom tetra?

The black phantom is smoky grey with black male fins and an oval shoulder patch; the red phantom is slightly smaller, translucent red, with a rounder black spot. Care is near-identical and the two make a classic combined display.

Sources & confidence

Sources & confidence (9 species)

These back the Black Phantom 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.

• Black Phantom Tetra Hyphessobrycon megalopterus — Seriously Fish (Hyphessobrycon megalopterus) high confidence
• Amano Shrimp Caridina multidentata — Aquarium Co-Op amano shrimp care; Aquadiction high confidence
• Assassin Snail Anentome helena (Clea helena) — The Shrimp Farm (theshrimpfarm.com/posts/assassin-snail-care) high confidence
• Black Neon Tetra Hyphessobrycon herbertaxelrodi — Seriously Fish / Aqua-Fish (Hyphessobrycon herbertaxelrodi) high confidence
• Bronze Corydoras Corydoras aeneus — Seriously Fish (seriouslyfish.com/species/corydoras-aeneus) high confidence
• Cardinal Tetra Paracheirodon axelrodi — Seriously Fish (seriouslyfish.com/species/paracheirodon-axelrodi) high confidence
• Celestial Pearl Danio Celestichthys margaritatus — Seriously Fish (seriouslyfish.com/species/celestichthys-margaritatus) high confidence
• Checker Barb Oliotius oligolepis — Seriously Fish — Oliotius oligolepis (https://www.seriouslyfish.com/species/oliotius-oligolepis/) high confidence
• Cherry Barb Puntius titteya — Seriously Fish (Puntius titteya) seriouslyfish.com/species/puntius-titteya high confidence

Care-guide sources (6)

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 — Megalamphodus megalopterus — authority/year (Eigenmann 1915), current name after 2024 revalidation, family (Acestrorhamphidae), max 3.6 cm SL, temp 22–28 °C, pH 6.0–7.5, dH up to 18, range (Upper Paraguay & Guaporé basins), IUCN Least Concern, diet, trophic level 3.2, "groups of 5 or more / 60 cm" husbandry note, high resilience
• Seriously Fish — Hyphessobrycon megalopterus — family (Characidae), synonyms (Megalamphodus megalopterus, M. rogoaguae), type locality (Cáceres), still/sluggish floodplain Pantanal biotope, wild water (20–28 °C, pH 5.0–7.0, 18–215 ppm), 30–36 mm SL, 80×30 cm tank, group 8–10, "very peaceful," sexual dimorphism (male black fins / female deeper with reddish fins), egg-scatterer breeding with no parental care
• Wikipedia — Black phantom tetra — Eigenmann 1915, Megalamphodus genus history and 2024 revalidation / subfamily Megalamphodinae, max ~4.4 cm SL, Guaporé & Paraguay range, wet-season floodplain breeding, female reddish pelvic/anal/adipose fins, distinction from M. sweglesi
• AquariumStoreDepot — Black Phantom Tetra Care Guide — size to 4.5 cm, lifespan 3–5 yr, 20 gal minimum (reason: active swimmers + male display), temp 22–28 °C, pH 6.0–7.5, GH 2–18, "slow-motion boxing match" mock-fight, dark-substrate colour note, sexing by fin colour, long-finned-fish nipping warning, breeding setup, black-vs-red-phantom distinction
• Aquarium Co-Op — Care Guide for Red and Black Phantom Tetras — size 3.8 cm, temp 21–28 °C, pH 6.0–7.5, soft–moderate hardness, 15–20 gal, group 6+, sparring behaviour strongest "when there are plenty of ladies around," sexing, tank mates (avoid long-finned slow species), breeding
• aqua-fish.net — Black Phantom Tetra Care — size 4–5 cm, lifespan "usually 3–5 years," temp 23–27 °C, pH 6.0–7.2, hardness 2–10 dH, tank 75–90 cm, group 8–10, male "elegant fin-flaring displays," breeding (soft acidic, daybreak spawn, eggs hatch ~24–36 h), diet

More on Black Phantom 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 →