Black Neon Tetra (Hyphessobrycon herbertaxelrodi)

Meet the Black Neon Tetra

The Black Neon Tetra, Hyphessobrycon herbertaxelrodi, is a small South American freshwater tetra associated with the Paraguay River basin. It is recognised by a bright silver-white horizontal line above a broad black stripe and an orange-red eye accent. One purchase supplies one live fish in the selected dispatch grade; the grade is not a promise that the fish has reached its adult length.

FishBase records 3.2 cm standard length and the species' environmental data. Seriously Fish gives 3.5 cm standard length, an 80 × 30 cm minimum base and a group of at least 8–10. These figures use standard length, while the open-ended >3.5 cm dispatch option does not define whether it uses standard or total length; the retail grade and biological record are therefore not treated as equivalent.

This is a social animal, not a solitary decorative accent. The buying decision must allow for the completed group, stable tested water and open midwater room. Its peaceful label does not remove the need to screen every other species for adult size, group requirement, feeding pace and water overlap.

Planning figures

• Adult size: 3.5 cm standard length.
• Group: at least 8–10.
• Minimum base: 80 × 30 cm, about 72 litres.
• Species aquarium guidance: 20–28°C, pH 5.0–7.5, 1–12 dGH from Seriously Fish.

Choose a dispatch size, then plan for the full-grown fish

One purchase supplies one live fish in the selected dispatch grade. The size you select is the size supplied, not the adult size. The available numeric grades run from 2–2.5 cm to more than 3.5 cm.

Sex is guaranteed only when the selected option explicitly states male or female. This Black Neon Tetra listing has no sex-guaranteed option. Do not use colour, body depth, fin shape or the gallery to infer the sex of the animal dispatched. Those features can vary with condition, maturity, lighting and individual appearance.

If you are comparing this fish with other small characins, browse the current tetra collection. The Neon Tetra (Paracheirodon innesi) offers a different appearance to compare. Read its adult size, water requirements and group needs before deciding between species; this comparison does not establish compatibility.

Decide how many fish the aquarium can support before choosing a dispatch grade. A smaller fish is not a way to fit the species temporarily into an undersized tank because its adult requirements remain the same. If you already keep a partial shoal, count the existing fish, confirm their identity and review the total adult load before adding more. Complete a sustainable social plan rather than simply filling spare visual space.

• Sold unit: one selected fish.
• Dispatch grades: 2–2.5 cm, 2.5–3 cm, 3–3.5 cm and more than 3.5 cm.
• Adult planning length: 3.5 cm standard length.
• Social plan: at least 8–10 Black Neon Tetras.

Size choices describe the animal supplied, so read the size label rather than assuming all fish in a group will arrive at the same stage of growth. A small fish still needs food it can swallow and an intake it cannot enter. An established group can contain different-sized individuals, but watch the smaller fish at feeding and make sure they are not displaced from food or cover.

The contrasting stripes suit a planted display where movement matters as much as colour. Its Paraguay River basin origin helps explain the appeal of wood, sand and planting, although a home aquarium need not imitate a particular stretch of river. Choose a layout that supports the fish and remains practical to maintain. A heavily decorated aquarium can look spacious from outside while offering little uninterrupted swimming room.

For a first shoaling species, the commitment is to the whole group and its mature aquarium. Think through space, water testing and maintenance before selecting a size. An established aquarist adding to a group should review the other residents too: a community suitable when all fish were juveniles may need more room as they mature.

Build the aquarium around swimming space and cover

Use a mature aquarium with a base of about 80 × 30 cm and a volume near 72 litres as the starting point for a small shoal. The footprint matters because this tetra is active: open mid-water swimming room is more useful than a tall but narrow vessel. Increase the plan when the shoal is larger, when other quick swimmers share the same level, or when hardscape substantially reduces open water.

Lay out distinct zones

Keep a clear swimming lane through the middle and upper water while using plants and wood around the sides and rear to create visual breaks. The aim is not to crowd the fish into cover; it is to let an individual move out of another fish's line of sight without losing the open space the shoal needs. Secure décor before filling the aquarium and leave access for cleaning around it.

Start with a properly matured system. The first tropical aquarium guide covers filter maturation and water testing. Maturation is about establishing the biological filter that processes waste, not merely letting tap water stand. The RSPCA aquarium guidance explains that fish release toxic ammonia, which a working biological filter converts first to nitrite and then to the safer nitrate.

Check the plan before adding fish

• Confirm that the base provides the required horizontal room.
• Reserve capacity for the whole shoal, not only the first individual.
• Position the filter outlet so the tank circulates without pinning fish in one area.
• Use a secure cover and close cable or pipe gaps.
• Make sure plants and décor do not block routine maintenance.

A larger aquarium does not remove the need for testing or compatible stocking, but it generally gives more dilution and more freedom to separate activity zones. When choosing between two tanks of similar volume, favour the one with the more useful base dimensions.

Understand the water ranges and keep conditions steady

Seriously Fish gives species aquarium guidance of 20–28°C, pH 5.0–7.5 and 1–12 dGH. FishBase separately records environmental values of 23–27°C and pH 5.5–7.5, with hardness up to 15 dH and no lower bound. An environmental record is not an instruction to recreate every recorded condition.

OATA's broad captive-bred tetra and pencilfish guidance is 22–27°C, pH 6.5–8.0 and 4–12 dH. It is not a species-specific optimum and its pH upper limit should not override this species profile. The shared interval of 23–27°C, pH 6.5–7.5 and 4–12 dGH is a practical comparison, not a newly established requirement. Assess suitability using species guidance; avoid abruptly changing an established healthy aquarium to chase a narrower figure.

Test the source water and the aquarium before choosing livestock. The water chemistry guide explains what pH, hardness and nitrogen readings mean, while the water matcher helps compare measured values with the range. Test with actual numbers; words such as soft, medium or hard can conceal large local differences.

Use nitrogen readings as action signals

OATA's tetra guidance sets ammonia and nitrite at zero and advises nitrate no more than 20 mg per litre above the normal tap-water level. The comparison with tap water matters: test both so a source-water contribution is not mistaken for an aquarium-only problem.

Change water often enough to hold these readings stable, using conditioned replacement water close to the aquarium's temperature and chemistry. Avoid sudden, large shifts. Record results so gradual change can be noticed before behaviour or appetite deteriorates.

Separate hardness from buffering

General hardness describes dissolved calcium and magnesium, while carbonate hardness helps indicate resistance to pH change. OATA's 3–10 dKH guidance applies broadly to the group, rather than establishing an individual requirement for this species. A pH reading alone does not tell you either kind of hardness. Keep test units with your notes so results remain comparable when you change a test kit or discuss the aquarium with a retailer.

If source water is unsuitable, work out a repeatable preparation method before acquiring fish. Each water change needs a consistent supply that you can test and prepare reliably. Altering pH without understanding the underlying water can create a cycle of adjustments. Ask for advice with source-water and aquarium readings rather than describing water only as hard or soft.

Run filtration for the whole shoal and community

Choose filtration for the final livestock plan, not only the fish bought first. Seriously Fish gives a turnover of four to five times aquarium volume per hour for this species profile; for a 72-litre aquarium that corresponds to roughly 290–360 litres per hour. Treat the stated flow as a planning reference and assess the actual current after media, pipework and décor reduce output.

Biological media needs oxygenated water and time to establish. Preserve mature biological media during service and rinse it gently in removed aquarium water when cleaning is necessary. Keep the filter operating continuously outside brief routine maintenance. If flow drops, inspect the intake, impeller and clogged mechanical media before assuming the unit is too small.

Balance circulation with usable swimming room

A turnover number alone cannot show where the current travels. Watch the entire shoal. Fish should be able to occupy the tank rather than being pushed into one sheltered corner, and waste should not settle throughout dead areas. Redirect the outlet or hardscape when circulation is uneven, while retaining the open lane used for social swimming.

• Check that every intake is protected and unobstructed.
• Service mechanical media when flow visibly declines.
• Preserve mature biological media during routine cleaning.
• Test ammonia and nitrite after a filter interruption or major service.
• Keep an aeration and temperature contingency for power or equipment failure.

More fish create more waste, so increasing the shoal or adding community species changes the filtration and maintenance requirement. A filter label cannot compensate for overstocking. Use observed behaviour, measured water quality and accumulated waste to judge whether the system is coping.

Recheck circulation after plants grow, filter media is serviced or the livestock plan changes. A flow figure describes pump capacity, while the fish reveal whether the resulting current is usable. Record the filter service date beside the water results so a gradual fall in flow can be distinguished from an abrupt equipment fault.

Feed small varied portions without burdening the filter

Offer a varied diet appropriate for a small tetra. Seriously Fish recommends varied dried foods and small live or frozen foods such as bloodworm, mosquito larvae, Daphnia and Moina. Choose particles the fish can take easily in mid-water; a food that is nutritionally suitable but too large is not useful.

OATA's tetra guidance recommends feeding only what the fish can eat within a few minutes, once a day. Start with a modest portion and watch whether every fish can feed. Remove or reduce food when particles pass through the group and settle. The correct portion is the amount the shoal consumes without leaving a residue that decomposes in the aquarium.

Make feeding an observation period

• Spread the food across the shoal rather than placing one dense pile.
• Check whether timid fish reach food before the quickest individuals take it.
• Note any fish that repeatedly isolates itself or misses meals.
• Rotate suitable prepared, frozen and live foods instead of relying on one item.
• Adjust the next portion when food remains or nitrate rises unusually.

Do not use extra food to solve competition caused by an unsuitable group or cramped layout. Distribute the same sensible ration more effectively. A second feeding point can help when one area is dominated, provided the total amount remains controlled.

Changes in appetite can signal stress, water-quality trouble or illness. Check temperature, ammonia, nitrite and recent changes before adding richer foods. If one fish cannot feed, observe its breathing, posture, swimming and interactions with the group, and contact us if the change persists or is accompanied by visible deterioration.

Keep a settled shoal with room to swim

Keep at least 8–10 Black Neon Tetras, and prefer ten or more where the aquarium can support them. Seriously Fish recommends at least 8–10 specimens; its mixed-sex suggestion gives guidance on group composition, while this offer provides no sex guarantee. FishBase records five or more and OATA gives five as a broad group minimum. Use the fuller species recommendation when planning this shoal.

The recommendation is a floor, not a promise that every group behaves identically. Use ten or more only where the aquarium footprint, filtration and total stocking allow. A fuller shoal can spread social attention, but crowding creates a different welfare problem. Count all adults at their 3.5 cm planning length when judging space.

Read patterns rather than one moment

Do not respond to persistent chasing by immediately adding unrelated species. Correct the shoal, space and layout first. If the aquarium cannot support a fuller group, the answer may be a different stocking plan rather than pushing the filter and space beyond their limits.

Observe at calm times as well as during feeding. Short displays and movement within the shoal are different from sustained exclusion, damage or inability to rest. Any torn fins or repeated cornering require prompt reassessment.

Observe condition without turning one sign into a diagnosis

A healthy Black Neon Tetra should be alert, balanced in the water and able to feed with the group. Use several observations together rather than treating one visual detail as a diagnosis. Colour can change with lighting, background, transport, social display and stress, so compare the fish with its normal appearance under ordinary aquarium conditions.

Begin with measured water and recent events. Check temperature, ammonia, nitrite and equipment, then review new livestock, missed maintenance, feeding and group interactions. OATA recommends watching swimming behaviour, colour, temperament, breathing, skin and fins, body condition and appetite because changes can provide an early warning that something needs attention.

Keep a useful baseline

• Record where the group normally rests and swims.
• Notice how quickly each fish approaches food.
• Compare breathing after the fish has settled.
• Keep recent test results and maintenance dates.
• Note repeated exclusion, hiding or missed meals.

When several fish change together, test the shared environment promptly. When one fish is affected, check its feeding access and interactions as well as the water. Provide cover and distribute food so the fish can rest and feed while the cause is assessed.

OATA advises testing water and contacting the retailer when livestock health causes concern. Share the measured values and observed changes, and seek appropriate veterinary help for persistent or worsening signs. This sequence gives the retailer or clinician useful information without turning a colour change or single missed meal into a diagnosis.

Introduce the fish carefully and monitor the first month

Be present to receive the parcel. Start filming before opening: show the sealed parcel and outer box, then open it in one continuous take and show the fish inside the sealed bag. Float the bag for 20–30 minutes before releasing the fish, and never pour the transport water into the aquarium. The current delivery and Live Arrival Guarantee policy sets out the claim conditions.

Prepare before the parcel arrives

• Confirm the aquarium is mature, heated and filtered.
• Test temperature, pH, ammonia and nitrite.
• Make sure the planned shoal and community fit the available capacity.
• Leave clear access for the arrival procedure.

After release, observe breathing, balance and the ability to join the group. Keep the first feeding small. Check ammonia and nitrite after introducing livestock because the biological load has changed, even when the filter was mature beforehand.

Use checkpoints instead of guesswork

During the first day, check posture, respiration and whether any fish is being persistently excluded. During the first week, record appetite, shoal interaction and nitrogen readings. By the first month, confirm that maintenance keeps nitrate controlled and that no companion repeatedly provokes or targets the tetras.

Do not make several major changes at once when a problem appears. Test water first, identify the immediate welfare risk, then adjust the relevant cause. This makes it easier to learn whether a change helped and avoids adding instability to an already stressed aquarium.

Maintain the aquarium with measured weekly checks

Use a repeatable maintenance routine built around test results and observation. OATA's tetra guidance strongly recommends this routine: at least once every week, carry out a partial water change of 25%. Test the water at least weekly.

Prepare replacement water before disturbing the tank

Treat tap water with a conditioner that removes chlorine or chloramine before it enters the aquarium. Bring it close to the aquarium's temperature and avoid a sudden change in pH or hardness. Siphon solid waste from accessible substrate while leaving enough undisturbed habitat for the fish to settle quickly after maintenance.

Check the filter for blockage. When media needs cleaning, OATA says not to run it under the tap; rinse it lightly in water removed from the aquarium so less of the established bacterial population is lost. Restore the equipment, confirm flow and re-check temperature before finishing.

Record the result, not only the task

• Write down ammonia, nitrite, nitrate, temperature and pH.
• Compare the aquarium nitrate with the source-water reading.
• Note flow changes, trapped debris and uneaten food.
• Check eyes, fins, scales, breathing, colour, body condition and appetite.
• Record any repeated chasing or separation from the shoal.

If ammonia or nitrite is detectable, respond to the water-quality problem before adding livestock. The RSPCA aquarium guidance explains why a mature biological filter is essential for processing toxic waste. A maintenance checklist should reveal trends before the shoal becomes distressed.

Arrange cover around the Black Neon Tetra's swimming route

The species profile offers two practical aquarium styles: a sandy substrate with driftwood roots and branches, or a heavily planted layout. Either can work when the centre and front retain an open route for the group. The objective is not to copy a photograph, but to combine security at the margins with enough clear water for normal movement.

Dried leaf litter can add cover and a natural tone. As it decomposes it supports microbial growth that may be grazed by fish and fry, but it also becomes part of the maintenance load. Use only aquarium-safe leaves, add them gradually and remove excessive material before it blocks flow or traps large amounts of food. Wood should be stable, smooth enough not to injure fish and positioned so waste can still be siphoned.

Use planting deliberately

• Place taller stems and broad leaves at the rear and sides.
• Keep a clear midwater route rather than filling every centimetre with foliage.
• Use subdued or floating cover only where it does not prevent surface gas exchange.
• Check that small dispatch-grade fish cannot enter an unsafe filter intake or hardscape gap.

The Black Neon Tetra is an egg-scattering free spawner with no parental care. That fact explains why occasional fry are possible in a mature, densely structured aquarium, but the product is not sold as a breeding group and no sex ratio is guaranteed. For a controlled spawning attempt, Seriously Fish describes a smaller, very dimly lit aquarium containing mature water, with mesh that lets eggs fall through while excluding adults. Fine-leaved plants or spawning mops offer another approach. Egg protection matters because this free-spawning species provides no parental care.

Prioritise the established group, stable water and easy maintenance. A beautiful natural-looking layout is successful only when the keeper can still inspect every fish, distribute food and reach the substrate and filter for routine care.

Screen community companions by size, pace and behaviour

Black Neon Tetras are described as very peaceful, but that is only the start of compatibility screening. Complete the 8–10 fish group first, then assess each proposed companion for adult size, its own social number, feeding pace, swimming level and overlap with stable water. The aquarium must have room for all completed groups rather than the juveniles present today.

Seriously Fish names similarly sized characids, hatchetfishes, pencilfishes, smaller callichthyid or loricariid catfishes and non-predatory small-to-medium cichlids as possible categories. These are prompts for species-level research, not universal guarantees.

Apply five checks

• Require a genuine water overlap rather than forcing either species to an avoidable edge.
• Reserve adult space and proper numbers for every social species.
• Avoid predators capable of swallowing small tetras and persistent bullies.
• Spread food so every group can feed without constant exclusion.
• Watch hiding, fin condition, breathing and group cohesion after introduction.

Related products are choices to compare rather than a compatibility promise.

Plan each social group independently

Another tetra shoal cannot replace companions of this species. Reserve sufficient numbers and space for every social species. A collection of isolated individuals may look varied but does not meet their different needs. Research each proposed fish's eventual size rather than only the size seen in a shop.

Sharing a swimming level is not automatically a problem, but several active groups may need a larger footprint and feeding area. Bottom-dwelling catfishes still contribute to waste and have their own feeding requirements. They should not be selected as cleaners or expected to live on leftovers. A non-predatory cichlid still needs assessment for adult behaviour and territorial space.

After introduction, observe existing residents and newcomers. Repeated cornering, damaged fins or inability to feed are reasons to reassess the arrangement. Provide observations and water readings when asking for help. More species or food cannot solve a lack of safe resting space.

Common questions about keeping this shoal

How big do Black Neon Tetras get?

Seriously Fish gives about 3.5 cm standard length; FishBase records 3.2 cm SL. Standard length excludes the tail fin and is distinct from a retail size grade.

What size aquarium do Black Neon Tetras need?

Seriously Fish recommends a base of at least 80 × 30 cm or equivalent, associated with about 72 litres. Allow more space for a larger shoal or additional residents.

How many Black Neon Tetras should I keep together?

Plan at least 8–10 using the species-specific Seriously Fish advice. The aquarium must support the full shoal and any other residents.

Are Black Neon Tetras suitable for beginners?

They can suit a beginner with a mature filtered aquarium, regular water testing and a proper shoal. Their peaceful behaviour does not remove those responsibilities.

What do Black Neon Tetras eat?

Offer suitably sized quality flakes or granules with varied small live or frozen foods such as Daphnia, Moina or bloodworm. OATA's broad tetra advice is a modest daily portion eaten within a few minutes.

What temperature, pH and hardness do Black Neon Tetras need?

Seriously Fish gives species aquarium guidance of 20–28°C, pH 5.0–7.5 and 1–12 dGH. OATA's tetra and pencilfish advice is broad group guidance, not a species optimum. Keep suitable conditions steady.

Are Black Neon Tetras aggressive or likely to nip fins?

Seriously Fish describes them as very peaceful. Persistent chasing, damaged fins or exclusion from food still need attention to space, group size and companions.

What kinds of fish can live with them?

The species profile suggests similarly sized characids, hatchetfishes, pencilfishes, smaller callichthyid or loricariid catfishes and non-predatory small-to-medium cichlids. Check each exact species' adult space, social needs and water.

How do Black Neon Tetras arrive alive in the UK?

Tropical Fish Co uses oxygen-filled bags and insulated packing, with a heat pack when weather calls for it, and a licensed live-animal courier. Be present, inspect the fish the same day and film continuously from the sealed parcel through opening to the fish in the sealed bag. Float the bag for 20–30 minutes before release and never pour transport water into the aquarium.

Sources for identity, care and welfare

FishBase: Hyphessobrycon herbertaxelrodi identity, distribution, environment, diet and maximum standard length.

Seriously Fish: Hyphessobrycon herbertaxelrodi species profile for aquarium footprint, water, feeding, behaviour and group care.

OATA: broad UK tetra guidance, explicitly not a species optimum.

RSPCA: general filter and aquarium-welfare guidance.

Tropical Fish Co: current delivery and Live Arrival Guarantee instructions.