Diamond Tetra Care Guide

The diamond tetra is a larger, deeper-bodied tetra whose famous prismatic sparkle is not there in the shop — juveniles look plain silver and only "switch on" the glitter with age, at around nine months, and a good varied diet. It is a peaceful, hardy community shoaler that will only mildly nip fins when kept in too small a group, and although it is Endangered in the wild, the trade fish are tank-bred, so buying captive-bred is the easy, responsible choice.

Diamond Tetra at a glance

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

Where it comes from

It is endemic to the Lake Valencia basin in northern Venezuela — the lake itself and its tributary streams, an extremely restricted natural range for a common aquarium fish. The native habitat is shallow, densely vegetated lake margins and slow streams full of plants and leaf litter, soft to moderately hard and slightly acidic to neutral, not extreme blackwater. That biotope translates straight into the tank: plant the edges densely but leave an open central lane, keep the flow gentle, and aim below neutral for the deepest colour. The conservation backdrop is the unusual part — the species has all but vanished from Lake Valencia itself to urban growth and pollution, yet it is bred in huge numbers for export, so the hobby population is in effect an ark for a fish disappearing in nature.

Did you know?

• The "diamond" is glitter that has to grow in: the prismatic sparkle is structural scale colour that develops with maturity at around nine months, so drab silver juveniles transform into shimmering adults.
• It is Endangered in the wild yet common in the hobby — the species may have vanished from its namesake home, Lake Valencia in Venezuela, to urban pollution, so the aquarium population is effectively an ark for it.
• It is one of the larger, longer-lived starter tetras at about 6 cm and three to six years, outsizing and outlasting neons and cardinals as a durable centrepiece shoal.
• The species epithet honours the Swiss-Venezuelan naturalist Henri Pittier; it was described by Carl Eigenmann in 1920.
• Ichthyologists moved it to the genus Makunaima (family Acestrorhamphidae) in a 2020 reclassification, though the hobby still universally calls it Moenkhausia pittieri.

Tank size — and why

Around 20 US gallons over a 60–80 cm footprint is the practical floor, and longer is better. Unlike the nano tetras, the driver here is the fish itself: this is an active 6 cm shoaler, so it needs horizontal swimming room and bioload headroom as well as the space for a group of eight or more that dilutes its mild nipping. Treat the 10–15 gallon tanks some guides suggest as too tight for a proper shoal of a fish this size. Prioritise length over height — it is a mid-water swimmer that wants a long, open lane.

As a guide, a 20-gallon tank comfortably suits about 6–8 Diamond Tetra as a single-species display, leaving room for tankmates.

How big does it really get?

Full-grown Diamond Tetra reach about 6 cm (2.4 in) long, but they are usually sold at only about 2.5 cm (1 in) — a typical shop size (estimate). At full size, Diamond Tetra needs roughly a 20-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 20-gallon aquarium.

Water parameters in practice

Comfortable across 22–28 °C, with about 24–26 °C ideal. The best colour develops in soft, slightly acidic water — roughly pH 6.0 to 6.8 — but tank-bred stock is genuinely adaptable and survives in harder, more alkaline tap water up to about 7.5, so it is forgiving for a soft-water tetra. As with all tetras, stability matters more than chasing a perfect number: a mature, cycled tank with steady parameters and low nitrate shows the diamond sheen at its best. Breeding is the exception and needs much softer, more acidic water than day-to-day keeping.

Diet & feeding

An omnivore and micropredator that eats worms, crustaceans and insects in the wild. A good-quality micro or crushed flake and small sinking granules make the staple, varied with small live or frozen foods — bloodworm, daphnia, brine shrimp, cyclops and moina — which sharpen the colour, build condition and trigger spawning. A little plant matter is appreciated too, such as spirulina or blanched greens, and it will nibble soft plants. Feed small amounts once or twice a day; it is an active, competitive feeder that holds its own at mealtimes.

Gear & setup

A heater, a gentle-to-moderate filter and a planted layout with an open central swimming space suit it. Darker substrate deepens the contrast and shows off the prismatic scales, while driftwood, leaf litter and densely planted edges mimic the vegetated lake-margin biotope and break the sight-lines that channel mild nipping. It is an active mid-to-upper swimmer, so keep the tank covered.

Temperament & behaviour

A peaceful shoaling fish, calm toward both its own kind and other species — males display and posture among themselves but do no real damage. The one welfare nuance is conditional fin-nipping: a diamond tetra kept in too small a shoal directs its competitive energy outward at slow or long-finned tankmates, a tendency Seriously Fish says is rectified simply by keeping it in a group of six to eight or more. Kept properly it is a community fish without significant nipping concerns, not a serpae- or tiger-barb-grade aggressor — the label that fits is "peaceful, but mildly nippy if under-grouped."

Group & social needs

Keep a shoal: six is the bare minimum, but eight to ten or more is the real target precisely because a bigger group suppresses the mild fin-nipping and replaces skittishness with confident, sparkling display. Under-stocked diamonds are nervous, drab and nippier. Raising a group together also gives you the best shot at breeding, since compatible pairs form within a shoal of similar size and age.

Compatible tank mates (preview)

A short, engine-cleared shortlist — the species TankStocking's welfare engine clears with Diamond 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 Diamond Tetra's tankmate surface for now — a dedicated tank-mates guide can follow for high-demand species.

Breeding & sexing

Sexing is relatively easy once the fish mature: males are larger and slimmer, carry more of the reflective scales and grow elongated dorsal, anal and pelvic fins with a violet sheen, while females are deeper-bodied — especially when gravid — with shorter, almost clear fins. Breeding is rated moderate and is famously hit-or-miss, partly because the fish will spawn only with others of the same size and age, so the reliable route is to raise a group and let a pair form. Use a separate, dimly lit tank with very soft, acidic water (around pH 5.5–6.5, GH 1–5) at 27–29 °C and fine-leaved plants or mops; the eggs are light-sensitive, so keep it dark. Parents eat the eggs, so remove the adults after spawning. Eggs hatch in roughly 24–36 hours; start the fry on infusoria, then baby brine shrimp.

Lifespan

Three to six years is the consistent figure with good care — longer-lived than a neon or cardinal, in keeping with its larger size. What shortens it is chronic stress in too small a group, unstable or dirty water, overfeeding, and being housed with fish that out-compete or harass it.

Common mistakes

• Rejecting drab shop juveniles as unhealthy. The diamond sparkle is structural colour that develops with maturity, at around nine months and on a good diet — a plain silver young fish is normal, not a defect, and there is no instant bling.
• Buying too few or too small a tank. Three to five fish in a 10-gallon nano turns skittish and nippier; this is a 6 cm active fish that wants eight or more and a 60–80 cm tank.
• Treating it as aggressive. It is peaceful; the nipping is a side-effect of under-grouping, fixable with a bigger shoal — do not over-restrict its tankmates as if it were a tiger barb.
• Pairing it with slow, long-finned fish. The conditional nipping is aimed here, so avoid bettas — including the peaceful Betta imbellis — fancy guppies, angelfish and long-finned gourami morphs.
• Keeping it with dwarf shrimp or tiny inverts you want to keep. An active 6 cm tetra will treat small shrimp and shrimplets as food.

Signs of trouble

• Loss of the diamond sparkle and a washed-out, drab look — usually stress from too small a group, unstable water or harassment.
• Clamped fins, hiding and isolation from the shoal — general stress or a water-quality problem.
• Frayed or nipped fins within the group — a sign the shoal is too small; raise the numbers to spread the nipping inward.
• Erratic swimming or flicking against décor — early irritation or the onset of white spot, typically stress-driven.

Is this fish right for you?

Do not buy diamond tetras if you cannot house a group of at least eight in a roughly 20-gallon, 60–80 cm tank, or if your community is built around delicate long-finned fish whose fins the conditional nipping would target. Skip them if you wanted instant colour from store-size juveniles, because the sparkle takes months to arrive. On sourcing, the fish is IUCN Endangered and nearly gone from Lake Valencia, but the trade is supplied entirely by captive breeding — so buying tank-bred diamonds is both the norm and the responsible choice, and it puts no pressure on the wild remnant. Avoid any dyed or painted fish, which is a welfare red flag.

Bringing one home

Acclimate the fish gently into a mature, stable tank — float to match temperature, then add tank water gradually over fifteen to twenty minutes before netting it across and leaving the shop water behind. Quarantine new stock, and settle the whole group at once over dark substrate with planting so the shoal forms quickly; remember the colour will keep deepening for months as the fish mature.

Common questions

Why is my diamond tetra not sparkly / dull and silver?

Because the sparkle develops with age. Shop juveniles are plain silver and the prismatic diamond sheen only switches on with maturity — at around nine months — and a good varied diet. A drab young fish is completely normal, not a defect or a sign of poor health.

Are diamond tetras aggressive or fin-nippers?

They are peaceful, with one caveat: kept in too small a group they can mildly nip fins, a tendency that disappears once they are in a proper shoal of eight or more. They are not tiger-barb-grade aggressors. Keep the group large and avoid slow, long-finned tankmates such as bettas, fancy guppies and angelfish.

How many diamond tetras should I keep, and what tank size?

Six is the bare minimum, eight to ten or more is the real target, specifically because a larger shoal suppresses the mild nipping. Plan for roughly 20 gallons over a 60–80 cm footprint — this is an active 6 cm fish, so the smaller nano tanks some guides cite are too tight.

Are diamond tetras endangered, and is it ethical to buy them?

The species is IUCN Endangered and has nearly disappeared from Lake Valencia in Venezuela, but the trade is supplied by captive breeding, not wild collection. So buying tank-bred diamond tetras is both the normal and the responsible choice — it puts no pressure on the wild remnant.

What water do diamond tetras need?

About 24–26 °C and soft, slightly acidic water (pH ~6.0–6.8) for the best colour, though tank-bred stock adapts to harder, neutral water up to about 7.5. Stability matters more than a perfect number — keep a mature, cycled tank with low nitrate.

Sources & confidence

Sources & confidence (9 species)

These back the Diamond 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.

• Diamond Tetra Moenkhausia pittieri — Seriously Fish (Moenkhausia pittieri) 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
• 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
• Checker Barb Oliotius oligolepis — Seriously Fish — Oliotius oligolepis (https://www.seriouslyfish.com/species/oliotius-oligolepis/) high confidence

Care-guide sources (5)

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 — Makunaima (Moenkhausia) pittieri — Eigenmann 1920, current genus Makunaima / family Acestrorhamphidae, max 6.0 cm SL, temp 24–28 °C, pH 6.0–7.0, dH 5–12, Lake Valencia basin range, IUCN Endangered (assessed Nov 2022), trophic level 3.2 (worms/crustaceans/insects), groups of 5+/80 cm
• Seriously Fish — Moenkhausia pittieri — family Characidae, endemic to Lake Valencia, biotope, 6 cm SL, temp 24–28 °C, pH 5.5–7.0, dH 5–12, 60×37.5×30 cm tank, best colour below neutral / tank-bred survive alkaline, fin-nipping rectified by shoal of 6–8, sexing, breeding parameters, juveniles bland silvery → sparkle with maturity
• Wikipedia — Diamond tetra — Eigenmann 1920, 2020 reclassification to Makunaima (Terán, Benítez & Mirande), endemic to Lake Valencia (Carabobo/Aragua), IUCN Endangered and "disappeared completely from Lake Valencia", 6.0 cm SL, male sexual dimorphism, bred for export
• AquariumSource — Diamond Tetra 101 — lifespan 3–6 yr, 2–2.4 in, ~15 gal small-group rationale, temp 72–82 °F, pH 6.0–7.5, peaceful without significant fin-nipping concerns, tank mates (shrimp eaten), diet incl. veg, breeding hit-or-miss / same size and age, iridescence develops ~9 months
• aqua-fish.net — Diamond Tetra — temp 24–28 °C, pH 5.5–7, hardness 5–12, long 60–75 cm tank, peaceful toward own and other species, school of 8–10, sexing, soft acidic dim breeding with light-sensitive eggs hatching ~24–36 h, lifespan 3–5 yr, varied diet

More on Diamond 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 →