Photo: Staatliche Naturwissenschaftliche Sammlungen Bayerns (CC BY-SA 3.0) — via Wikimedia Commons
Costa's Tetra (Moenkhausia costae)
A slender, active shoaling tetra from Brazil with a striking black slash through its tail — easy to keep and fast to school.
Will it live with a Costa's Tetra?
We compare each fish against your costa's tetra on temperament, size, water parameters and swimming zone. Set your tank size and filter the results.
- Agassiz's Corydoras✅ CompatiblePeaceful · 6 cm · Easy care · 22–28 °C (72–82 °F)
- Both are peaceful, and their water overlaps around 22–28 °C — no size, zone or temperament conflicts.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Agassiz's Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Bamboo Shrimp✅ CompatiblePeaceful · 8 cm · Medium care · 22–27 °C (72–81 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Betta✅ CompatibleSemi-aggressive · 6.5 cm · Easy care · 24–28 °C (75–82 °F)
- Peaceful + Semi-aggressive, but with no direct clash here, and their water overlaps around 24–28 °C — no size, zone or temperament conflicts.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Black Kuhli Loach✅ CompatiblePeaceful · 8 cm · Easy care · 23–28 °C (73–82 °F)
- Compatible on the things that matter: shared water near 23–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Black Skirt Tetra✅ CompatibleSemi-aggressive · 6 cm · Easy care · 20–26 °C (68–79 °F)
- Peaceful + Semi-aggressive, but with no direct clash here, and their water overlaps around 22–26 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Black Skirt Tetra in a shoal of 6+ or it gets stressed and nippy.
- Blackline Rasbora✅ CompatiblePeaceful · 6 cm · Easy care · 22–28 °C (72–82 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Blackline Rasbora in a shoal of 6+ or it gets stressed and nippy.
- Blood Red Tiger Pleco✅ CompatiblePeaceful · 6 cm · Medium care · 24–29 °C (75–84 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Bolivian Ram✅ CompatiblePeaceful · 8 cm · Medium care · 24–28 °C (75–82 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Butterfly Hillstream Loach✅ CompatiblePeaceful · 6 cm · Hard care · 18–24 °C (64–75 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Celebes Rainbowfish✅ CompatiblePeaceful · 7 cm · Medium care · 22–28 °C (72–82 °F)
- Compatible on the things that matter: shared water near 22–28 °C, workable temperaments, and no predator-and-prey size gap.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Celebes Rainbowfish in a shoal of 6+ or it gets stressed and nippy.
- Corydoras Catfish✅ CompatiblePeaceful · 6.5 cm · Easy care · 22–26 °C (72–79 °F)
- Compatible on the things that matter: shared water near 22–26 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Corydoras Catfish in a shoal of 6+ or it gets stressed and nippy.
- Croaking Gourami✅ CompatiblePeaceful · 7 cm · Easy care · 24–28 °C (75–82 °F)
- Compatible on the things that matter: shared water near 24–28 °C, workable temperaments, and no predator-and-prey size gap.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Desert Goby✅ CompatibleSemi-aggressive · 6 cm · Easy care · 18–28 °C (64–82 °F)
- Compatible on the things that matter: shared water near 22–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Diamond Tetra✅ CompatiblePeaceful · 6 cm · Easy care · 22–28 °C (72–82 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Diamond Tetra in a shoal of 6+ or it gets stressed and nippy.
- Eastern Betta✅ CompatibleSemi-aggressive · 6 cm · Medium care · 24–28 °C (75–82 °F)
- Compatible on the things that matter: shared water near 24–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Elegant Cory✅ CompatiblePeaceful · 6 cm · Easy care · 22–28 °C (72–82 °F)
- Compatible on the things that matter: shared water near 22–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Elegant Cory in a shoal of 6+ or it gets stressed and nippy.
- Gold Barb✅ CompatiblePeaceful · 7.5 cm · Easy care · 18–26 °C (64–79 °F)
- Both are peaceful, and their water overlaps around 22–26 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Gold Barb in a shoal of 6+ or it gets stressed and nippy.
- Peacock Gudgeon✅ CompatiblePeaceful · 7 cm · Medium care · 22–28 °C (72–82 °F)
- Both are peaceful, and their water overlaps around 22–28 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Peppered Corydoras✅ CompatiblePeaceful · 7 cm · Easy care · 18–26 °C (64–79 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Peppered Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Rio Negro Checkerboard Cichlid✅ CompatiblePeaceful · 7 cm · Hard care · 24–29 °C (75–84 °F)
- Both are peaceful, and their water overlaps around 24–28 °C — no size, zone or temperament conflicts.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Splashing Tetra✅ CompatiblePeaceful · 8 cm · Medium care · 22–28 °C (72–82 °F)
- Both are peaceful, and their water overlaps around 22–28 °C — no size, zone or temperament conflicts.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Splashing Tetra in a shoal of 6+ or it gets stressed and nippy.
- Spotfin Corydoras✅ CompatiblePeaceful · 6.5 cm · Easy care · 22–26 °C (72–79 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Spotfin Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Spotted Corydoras✅ CompatiblePeaceful · 7 cm · Easy care · 22–27 °C (72–81 °F)
- Both are peaceful, and their water overlaps around 22–27 °C — no size, zone or temperament conflicts.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Spotted Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Sterbai Corydoras✅ CompatiblePeaceful · 6.5 cm · Medium care · 24–30 °C (75–86 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Sterbai Corydoras in a shoal of 6+ or it gets stressed and nippy.
- African Butterfly Cichlid⚠️ With cautionSemi-aggressive · 8 cm · Medium care · 22–28 °C (72–82 °F)
- African Butterfly Cichlid is semi-aggressive and may chase or nip the smaller Costa's Tetra — plant heavily and break up sight lines.
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Amazon Puffer⚠️ With cautionPeaceful · 8 cm · Medium care · 23–28 °C (73–82 °F)
- Your 75 L tank is below the ~120 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Amazon Puffer in a shoal of 6+ or it gets stressed and nippy.
- Ash Lipped Apisto⚠️ With cautionSemi-aggressive · 7 cm · Hard care · 24–29 °C (75–84 °F)
- Ash Lipped Apisto and Costa's Tetra are close in size, but the semi-aggressive one tends to dominate — add costa's tetra in a group to spread the pressure.
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Banded Dwarf Cichlid⚠️ With cautionSemi-aggressive · 7 cm · Medium care · 24–30 °C (75–86 °F)
- Expect Banded Dwarf Cichlid to harass Costa's Tetra at times; give dense cover and watch them at feeding.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Bleeding Heart Tetra⚠️ With cautionSemi-aggressive · 7 cm · Medium care · 23–28 °C (73–82 °F)
- Bleeding Heart Tetra is semi-aggressive and may chase or nip the smaller Costa's Tetra — plant heavily and break up sight lines.
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Bleeding Heart Tetra in a shoal of 6+ or it gets stressed and nippy.
- Bright Diamond Tetra⚠️ With cautionPeaceful · 7 cm · Hard care · 24–28 °C (75–82 °F)
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Bright Diamond Tetra in a shoal of 8+ or it gets stressed and nippy.
- Buenos Aires Tetra⚠️ With cautionSemi-aggressive · 7 cm · Easy care · 18–26 °C (64–79 °F)
- Buenos Aires Tetra is semi-aggressive and may chase or nip the smaller Costa's Tetra — plant heavily and break up sight lines.
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Buenos Aires Tetra in a shoal of 6+ or it gets stressed and nippy.
- Colombian Tetra⚠️ With cautionSemi-aggressive · 6.5 cm · Easy care · 24–28 °C (75–82 °F)
- Your 75 L tank is below the ~114 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Colombian Tetra in a shoal of 6+ or it gets stressed and nippy.
- Hongsloi Dwarf Cichlid⚠️ With cautionSemi-aggressive · 7 cm · Medium care · 24–29 °C (75–84 °F)
- Hongsloi Dwarf Cichlid is semi-aggressive and may chase or nip the smaller Costa's Tetra — plant heavily and break up sight lines.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Mahachai Betta⚠️ With cautionAggressive · 7 cm · Medium care · 24–30 °C (75–86 °F)
- Expect Mahachai Betta to harass Costa's Tetra at times; give dense cover and watch them at feeding.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Melon Barb⚠️ With cautionPeaceful · 7 cm · Easy care · 22–28 °C (72–82 °F)
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Melon Barb in a shoal of 8+ or it gets stressed and nippy.
- Rounded Filament Barb⚠️ With cautionPeaceful · 7 cm · Medium care · 22–27 °C (72–81 °F)
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Rounded Filament Barb in a shoal of 6+ or it gets stressed and nippy.
- Roundtail Paradise Fish⚠️ With cautionSemi-aggressive · 7 cm · Easy care · 10–26 °C (50–79 °F)
- Expect Roundtail Paradise Fish to harass Costa's Tetra at times; give dense cover and watch them at feeding.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Sumo Loach⚠️ With cautionSemi-aggressive · 7 cm · Medium care · 22–26 °C (72–79 °F)
- Sumo Loach and Costa's Tetra are close in size, but the semi-aggressive one tends to dominate — add costa's tetra in a group to spread the pressure.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Tiger Barb⚠️ With cautionSemi-aggressive · 7 cm · Easy care · 22–28 °C (72–82 °F)
- Tiger Barb and Costa's Tetra are close in size, but the semi-aggressive one tends to dominate — add costa's tetra in a group to spread the pressure.
- Your 75 L tank is below the ~95 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Tiger Barb in a shoal of 6+ or it gets stressed and nippy.
- Umbrella Dwarf Cichlid⚠️ With cautionSemi-aggressive · 7 cm · Medium care · 20–26 °C (68–79 °F)
- Umbrella Dwarf Cichlid is semi-aggressive and may chase or nip the smaller Costa's Tetra — plant heavily and break up sight lines.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Alligator Gar⛔ Not recommendedAggressive · 250 cm · Hard care · 24–28 °C (75–82 °F)
- Size gap is too large (250 vs 7 cm): Alligator Gar will treat Costa's Tetra as food.
- Alligator Gar clearly outsizes Costa's Tetra and is aggressive; risky unless the tank is big and well-planted.
- Your 75 L tank is below the ~3785 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Clown Knifefish⛔ Not recommendedAggressive · 90 cm · Hard care · 24–28 °C (75–82 °F)
- Clown Knifefish (90 cm) is big enough to swallow the 7 cm Costa's Tetra whole.
- Clown Knifefish is aggressive and may chase or nip the smaller Costa's Tetra — plant heavily and break up sight lines.
- Your 75 L tank is below the ~750 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Fire Eel⛔ Not recommendedSemi-aggressive · 100 cm · Medium care · 24–28 °C (75–82 °F)
- Costa's Tetra is bite-sized to a 100 cm predatory fire eel — it will be eaten.
- Expect Fire Eel to harass Costa's Tetra at times; give dense cover and watch them at feeding.
- Your 75 L tank is below the ~380 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Koi⛔ Not recommendedPeaceful · 90 cm · Medium care · 4–28 °C (39–82 °F)
- Size gap is too large (90 vs 7 cm): Koi will treat Costa's Tetra as food.
- Your 75 L tank is below the ~3800 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Redtail Catfish⛔ Not recommendedAggressive · 120 cm · Hard care · 24–27 °C (75–81 °F)
- Redtail Catfish (120 cm) is big enough to swallow the 7 cm Costa's Tetra whole.
- Expect Redtail Catfish to harass Costa's Tetra at times; give dense cover and watch them at feeding.
- Your 75 L tank is below the ~5700 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Spotted Gar⛔ Not recommendedAggressive · 90 cm · Hard care · 18–26 °C (64–79 °F)
- Costa's Tetra is bite-sized to a 90 cm predatory spotted gar — it will be eaten.
- Expect Spotted Gar to harass Costa's Tetra at times; give dense cover and watch them at feeding.
- Your 75 L tank is below the ~600 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Wels Catfish⛔ Not recommendedAggressive · 300 cm · Hard care · 15–25 °C (59–77 °F)
- Costa's Tetra is bite-sized to a 300 cm predatory wels catfish — it will be eaten.
- Wels Catfish clearly outsizes Costa's Tetra and is aggressive; risky unless the tank is big and well-planted.
- Your 75 L tank is below the ~20000 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
- Wolf Cichlid⛔ Not recommendedAggressive · 72 cm · Hard care · 24–30 °C (75–86 °F)
- Wolf Cichlid (72 cm) is big enough to swallow the 7 cm Costa's Tetra whole.
- Expect Wolf Cichlid to harass Costa's Tetra at times; give dense cover and watch them at feeding.
- Your 75 L tank is below the ~760 L this pairing really wants — crowding raises aggression.
- Keep Costa's Tetra in a shoal of 6+ or it gets stressed and nippy.
Compatibility is computed from each species' care data — a strong starting point, not a guarantee. Individual temperament varies, so always introduce new fish slowly and watch them.
Costa's Tetra care specs
- Care level
- Easy
- Breeding
- Hard
- Max size
- 7 cm (2.8 in)
- Min tank size
- 75 L (19.8 gal)
- Temperature
- 22–28 °C (72–82 °F)
- pH
- 6–7.5
- Hardness
- 2–15 dGH
- Lifespan
- 3–5 years
- Diet
- Omnivore
- Swim level
- Middle
- Group size
- 6+ (shoaling)
- Family
- Characidae
- Origin
- Brazil — São Francisco and Itapicuru river basins
What is a Costa’s Tetra?
The Costa’s Tetra (Moenkhausia costae) is a slender, energetic characin endemic to northeastern Brazil. It reaches up to 7 cm (2.75 in) — on the larger end for a community tetra — and carries a clean silvery-green sheen along its flanks. The feature that makes it instantly recognisable is a bold diagonal black stripe that cuts through the lower caudal fin, earning it the common trade name “Blackline Tail Tetra.” Under bright lighting, that tail stripe flickers in a tight shoal like a synchronized signal, making the species as visually compelling in motion as any more colourful tetra.
Care is genuinely easy for an adult fishkeeper. The Costa’s Tetra tolerates a reasonable range of water conditions, accepts most prepared and frozen foods, and shows no aggression toward similarly sized peaceful companions. Its main requirement is social: it must be kept in a group, and that group must be large enough to trigger confident, cohesive schooling behaviour.
Where does the Costa’s Tetra come from?
Moenkhausia costae is native to the São Francisco and Itapicuru river basins of northeastern Brazil — a distinct biogeographic region separate from the Amazon proper. These drainages are characterised by warm, slow to moderately flowing water with varying degrees of dissolved tannins depending on season and location. Substrates in the native range are typically sandy or silty, with submerged leaf litter, root tangles and riparian vegetation providing shelter.
Knowing this origin points you toward sensible tank design: a setup with a dark substrate, subdued or dappled lighting, some tannin staining from driftwood or Indian almond leaves, and open midwater lanes for schooling will replicate the conditions under which this fish evolved to thrive.
What size tank does a Costa’s Tetra need?
The minimum recommended tank size is 75 litres (20 gallons), and that assumes a tightly managed group of six. For a more comfortable group of eight to ten — which is the preferred social configuration — aim for 100–120 litres (26–32 gallons). Because these are mid-column, open-water swimmers, prioritise a tank that is long and wide rather than tall: horizontal swimming length matters far more than depth for a schooling tetra.
Aquascape the tank to suit the fish’s natural habitat: plant the sides and back densely with fine-leaved or feathery species (Vallisneria, Cabomba, Java fern), leaving a clear central corridor for schooling. Dark substrate — black or dark brown sand — will contrast well with the silvery body and make the black tail stripe more visible. Add one or two pieces of driftwood for structure. Filtration should provide good turnover but without strong direct flow across the main swimming zone; these fish come from moderate-current rivers, not fast-flowing streams.
What water parameters does the Costa’s Tetra need?
- Temperature: 22–28 °C (72–82 °F). Mid-range is fine; avoid prolonged extremes at either end.
- pH: 6.0–7.5. Slightly acidic to neutral is the target zone; the species tolerates mildly alkaline conditions but does not thrive in them long-term.
- Hardness: 2–15 dGH. They accept moderately hard water, which makes them easier to keep in many tap-water-supplied tanks than more demanding softwater tetras.
Stability is more important than hitting an exact number. A well-cycled tank with consistent weekly water changes of 25–30% will keep parameters steady and fish healthy. Avoid rapid temperature swings — these are more stressful than a steady reading one or two degrees outside the ideal range.
What do Costa’s Tetras eat?
The Costa’s Tetra is an omnivore that accepts food readily at the middle of the water column. A quality small-pellet or flake staple covers their nutritional baseline. Rotate in frozen or live foods — bloodworms, daphnia, brine shrimp, and mosquito larvae — to condition colour, maintain vitality, and provide behavioural enrichment. They will also pick at micro-granules and finely crushed foods.
Feed small amounts two to three times daily, offering only what the group consumes within two to three minutes. Because they tend to be active and competitive at feeding time, broadcast food across the tank width rather than dropping it in one spot, which allows shyer individuals to feed without being outcompeted. Remove any uneaten food to keep water quality high.
Are Costa’s Tetras peaceful — and what fish can live with them?
The Costa’s Tetra is a peaceful community fish that co-exists well with a wide range of similarly sized and temperamented species. In a group of six or more they become confident and stay mid-column; in smaller numbers they become skittish and may nip at long-finned tank-mates such as angelfish or bettas. Keep the group at six minimum at all times.
Good companions include other small peaceful characins, rasboras, corydoras catfish, small loaches, and dwarf cichlids that occupy different tank zones without being aggressive. Avoid pairing them with large, predatory fish that could swallow them, or with fin-nipping species. Invertebrates such as Amano shrimp and nerite snails are safe; smaller ornamental shrimp may be at some risk from active, curious tetras.
For a full pairing guide — including species-by-species compatibility ratings — see Costa’s Tetra tank mates.
How do you tell male from female Costa’s Tetras?
Sexing Costa’s Tetras outside of breeding condition requires some patience. Females are notably deeper-bodied and plumper, particularly when carrying eggs — a gravid female has a distinctly rounded belly compared to the slim flanks of a male. Males are slimmer and more torpedo-shaped throughout their body. Colouration and finnage are not reliably different between sexes.
The distinction becomes much clearer when a group is conditioned for breeding: females noticeably fill out with eggs, and males may show more active posturing behaviour. In a resting mixed group, the easiest approach is to look at the belly profile from above — rounder individuals are almost always female.
How do Costa’s Tetras breed?
Breeding Moenkhausia costae is rated hard for home aquarists, consistent with many open-water egg-scattering characins. They are egg scatterers that provide no parental care, and the adults will eat eggs and fry if given the opportunity.
A dedicated breeding tank of around 30–40 litres (8–10 gallons) is recommended — bare-bottomed or with a fine mesh grid just above the base to catch eggs before adults reach them. Condition a proven pair or a small group with high-quality live and frozen foods over one to two weeks. Soft, slightly acidic water — pH 6.0–6.5, hardness at the low end of their range — and a temperature of around 26–27 °C (79–81 °F) can trigger spawning. Spawning typically occurs in morning light over fine-leaved plants or a spawning mop.
Remove adults immediately after spawning. Eggs hatch within 24–36 hours and fry become free-swimming a few days later. First foods are infusoria or commercially prepared fry foods; introduce newly hatched brine shrimp as they grow. Water quality during the fry stage must be pristine.
What diseases do Costa’s Tetras get?
The Costa’s Tetra is a hardy species with no unusual disease susceptibility, but it is vulnerable to the same common ailments as any freshwater characin. Ich (white-spot disease) is the most common, typically triggered by temperature instability or chilling during water changes. Velvet (Oodinium) can appear in newly established tanks. Fin rot is almost always a consequence of poor water quality. Neon tetra disease — a microsporidian infection that causes fading, curved spines and wasting — can affect Moenkhausia species; quarantine any new fish showing these signs immediately.
Prevention follows a standard protocol: quarantine all new fish for at least two weeks before adding them to your display tank, maintain a cycled, stable environment with regular partial water changes, and avoid temperature swings during maintenance.
Health note: this profile covers prevention only. For a sick fish, confirm the diagnosis against a reliable veterinary or fish-health resource before deciding on any course of treatment.
How long do Costa’s Tetras live?
A well-kept Costa’s Tetra lives 3–5 years. Consistent water quality, a varied diet, a group of at least six to keep the fish sociologically comfortable, and a tank sized appropriately for that group are the four factors most likely to keep them healthy to the upper end of that range. Stressors — poor water, isolation, overheating or chilling — compress lifespans noticeably in small tetras, so maintaining the fundamentals pays a direct return in longevity.
Frequently asked questions
How many Costa's Tetras should I keep together?
A minimum of 6 is the standard recommendation for any open-water shoaling tetra. Smaller numbers increase skittishness and can trigger fin-nipping. A group of 8–12 produces the most impressive schooling behaviour and keeps individuals calmer.
Is the Costa's Tetra the same as the Diamond Tetra?
No. Both are Moenkhausia tetras, but they are distinct species. The Diamond Tetra (Moenkhausia pittieri) has a deep, iridescent body and is larger; the Costa's Tetra is slimmer and identified by a diagonal black stripe through its caudal fin rather than body iridescence.
What you need to keep a costa's tetra
The baseline is a heated, filtered 75 L+ tank: a reliable heater to hold 22–28 °C (72–82 °F), a gentle filter that won't batter a costa's tetra in the current, and a tight-fitting lid. Cycle the tank fully before adding any fish.
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