Red-Line Tetra (Hyphessobrycon amapaensis)

Choose the Red-Line Tetra offer

Red-Line Tetra, Hyphessobrycon amapaensis, is a small, peaceful freshwater tetra for a carefully planned community aquarium. FishBase records a maximum length of 3 cm standard length, places it in the American-tetra family Acestrorhamphidae and records it from the type locality in Amapá, Brazil. It is benthopelagic in nature and inhabits small savanna creeks over sand and gravel.

This fish suits a keeper prepared to maintain a mature biological filter, test the water every week and build a proper shoal. Its peaceful temperament, small size and ability to thrive in a planted arrangement make it a candidate for a researched community, but its soft, acidic water range must overlap with every proposed companion. Browse our current tetra collection when comparing identities and group requirements.

Understand the purchase unit

One purchase supplies one animal in the selected size. The dispatch sizes are 2–2.5 cm and 2.5–3 cm; use the live size selector to see which size can be selected when you place the order. The size you select is the size supplied, not the adult size. Plan the aquarium and shoal around the maximum recorded length of 3 cm standard length rather than assuming that a smaller dispatch size changes the long-term care requirement.

Sex is guaranteed only when the selected option explicitly states male or female. This Red-Line Tetra listing has no sex-guaranteed option.

Some gallery images have been digitally enhanced to improve image quality. They show the listed type of animal rather than guaranteeing the exact markings of the individual supplied, so natural colour and pattern can vary.

Before choosing a delivery date, read the current delivery and Live Arrival Guarantee policy for the applicable dispatch, delivery and claim steps.

Plan around the decisive care figures

The decisive planning figures are the shoal size, aquarium footprint and water range. Seriously Fish recommends at least 8–10 specimens and says an aquarium with base dimensions of at least 60 × 30 cm, or an equivalent footprint, should be the smallest considered. Its reference volume for that footprint is approximately 54 litres. Treat the base dimensions as the first space test because a differently shaped aquarium can hold a similar volume without providing the same swimming length.

Make the decisions in the right order

1. Measure the aquarium base. A nominal volume alone does not answer whether the aquarium meets the 60 × 30 cm minimum footprint.
2. Test the settled aquarium water. Compare temperature, pH and general hardness with the full 23–28°C, pH 5.0–7.0 and 1–8 dGH range.
3. Reserve room for the group. Plan at least 8–10 Red-Line Tetras together rather than treating one small fish as a complete social unit.
4. Screen every companion. Match size, temperament, predation risk, water requirements and total use of the aquarium.
5. Confirm filtration and maintenance. The aquarium needs a mature biological filter, zero ammonia, zero nitrite and a weekly care routine.

A plan that fails any one of these tests needs revision before the fish is introduced. A long aquarium with compatible water but only two tetras does not meet the social requirement; a ten-fish group in water above pH 7.0 does not meet the stated water range. Use all the figures together.

Give the shoal enough usable space

Start with a base of at least 60 × 30 cm or an equivalent footprint and a reference volume of approximately 54 litres. This minimum is for planning the Red-Line Tetra group in a properly arranged aquarium, not permission to fill every part of that volume with livestock. Existing fish, decorations, plants, filtration equipment and the activity of other shoals all affect how much usable space remains.

Check shape before volume

Measure the internal swimming length and front-to-back width rather than relying only on the volume printed on the aquarium. A tall, narrow aquarium may approach 54 litres while failing to match a 60 × 30 cm base. A layout with the required footprint still needs clear swimming room alongside cover, so avoid filling the entire base with solid ornaments.

Balance cover with swimming room

Provide plants or suitable ornaments for shelter while preserving open space where the group can move together. OATA advises swimming space and a gentle current for smaller tetras, while the species profile supports both planted and wood-based arrangements. Position cover around parts of the rear, sides or base instead of creating a solid barrier across the full length.

Larger aquariums are useful when the extra footprint supports a bigger social group or reduces crowding from compatible companions. OATA also notes that larger aquariums tend to have more stable temperature and water quality. Extra litres do not replace weekly testing, maintenance or a mature filter, but they provide more room for a deliberate layout and reduce the pressure to fit several groups into the minimum footprint.

Match the full water range

Maintain 23–28°C, pH 5.0–7.0 and general hardness of 1–8 dGH. Seriously Fish also gives conductivity of 5–15 µS/cm for this tetra, but conductivity should not replace direct checks of temperature, pH and hardness. Test the established aquarium rather than relying on a regional tap-water description or a single old result.

Our aquarium water chemistry guide explains what the measurements represent. Once you have current readings, use the water matcher to compare them with the complete range.

Read the numbers together

A single matching number is not enough. If temperature fits but pH or hardness falls outside the range, revise the plan rather than describing the aquarium as suitable. Check prospective tank mates against the same readings so one fish is not kept at an unsuitable edge simply to accommodate another.

Keep the range in context

OATA's tetra and pencilfish sheet gives group guidance of 22–27°C, pH 6.5–8.0 and 4–12 dGH. Use the narrower Red-Line Tetra values above for this aquarium because they address this animal directly. OATA's water-quality targets remain useful for the wider group: ammonia and nitrite should both be zero, while nitrate should not exceed 20 mg per litre above the normal tap-water level.

Re-test after changes to stocking or maintenance because the aquarium is a working biological system. Record readings taken at the same stage of the weekly routine so trends are easier to recognise than they would be from occasional, unrelated tests.

Mature the filter before introduction

Use a well set up and maintained biological filter before any Red-Line Tetra enters the aquarium. The RSPCA explains that fish release toxic ammonia; beneficial bacteria in the filter convert it first to toxic nitrite and then to safer nitrate. A filter therefore needs time to establish its bacterial population, and clear-looking water is not a substitute for zero ammonia and zero nitrite test results.

If this is your first aquarium, follow our first tropical tank guide to prepare and mature the system before livestock is introduced. Testing establishes whether the filter is processing waste; the age of the aquarium by itself does not answer that question.

Size the circulation from the reference aquarium

For an aquarium of approximately 54 litres, Seriously Fish recommends turnover of four to five times the aquarium volume per hour and gives a filter rating of about 215–270 litres per hour. The arithmetic provides a useful check: 54 multiplied by four is 216, while 54 multiplied by five is 270. Position the return so the aquarium retains swimming room and the gentle current advised for smaller tetras.

For the same approximately 54-litre aquarium, Seriously Fish suggests roughly 75–100 W of heating to hold 23–28°C when the room is around 20°C. Preserve that room-temperature assumption when using the figure. Select and control the heater for the actual aquarium, then verify the result with a temperature reading rather than relying on wattage alone.

Protect water quality every week

Build the routine around weekly testing and a 25% partial water change at least once a week. OATA strongly recommends changing 25% at least once each week, testing at least weekly, treating replacement tap water for chlorine or chloramine and checking the filter for blockages. These actions protect the biological filter and limit the waste created by the whole aquarium.

Use one repeatable weekly sequence

1. Observe before disturbing the aquarium. Note swimming, breathing, colour, body condition and interest in food.
2. Test the water. Ammonia and nitrite should both be zero. Compare nitrate with the normal tap-water reading.
3. Change 25% at least once a week. A siphon can remove solid waste from the substrate while water is removed.
4. Condition the replacement water. Neutralise chlorine or chloramine before it enters the aquarium.
5. Check the filter. Clear blockages and confirm that circulation has returned to its normal pattern.
6. Clean media only when needed. Rinse it lightly in the removed aquarium water so tap-water disinfectants do not damage the bacterial population.

Calculate the nitrate ceiling correctly

OATA's nitrate figure is relative to the normal tap-water level: aquarium nitrate should not exceed that baseline by more than 20 mg per litre. If the tap water measures 10 mg per litre, the corresponding ceiling is 30 mg per litre. If the tap result is 25 mg per litre, the corresponding ceiling is 45 mg per litre. Measure the baseline rather than assuming it is zero.

Do not add more fish while ammonia or nitrite is above zero. Both indicate that waste processing is not keeping pace with the aquarium. Re-test after maintenance and review recent increases in livestock or feeding because OATA warns that stocking too quickly can leave too few nitrifying bacteria to process the additional waste.

Watch for hanging at the surface, sitting on the bottom, erratic swimming, unusually fast or slow gill movement, changed colour, increased hiding, white spots, fluffy growths, damaged fins or scales, altered body condition and reduced feeding. Test the water first when these changes appear, then contact us for health guidance rather than starting an unplanned treatment.

Feed small food once a day

Feed a varied omnivorous diet in particles small enough for a 3 cm tetra. Seriously Fish describes the natural diet as likely to include small invertebrates, crustaceans, filamentous algae and fallen fruit. In the aquarium, dried food alone may sustain the fish, but a varied menu should also contain suitably small live or frozen foods.

OATA recommends a good-quality flake or granule as the regular aquarium food for tetras and pencilfish, supplemented with small live or frozen items such as daphnia, small bloodworm or tubifex. Seriously Fish also names mosquito larvae, Daphnia, Moina and chironomid larvae, together with freeze-dried bloodworm and freeze-dried Daphnia.

Build a supported menu

Judge the portion by what disappears within a few minutes rather than by a fixed pinch or spoonful. If food remains after that period, offer less at the next feed. Overfeeding allows uneaten food to break down and release toxic waste, so portion control supports the zero-ammonia and zero-nitrite targets as directly as filter maintenance does.

Use feeding as an observation point

Watch the group while it eats. Reduced intake or a sudden lack of interest is one of OATA's warning signs and should prompt a water test alongside checks of swimming, breathing, colour and body condition. The aim is not to force extra food into a reluctant fish; it is to recognise a change early while protecting water quality.

Match particle size to the mouth of the fish. The dispatch size can be as small as 2 cm, so inspect the food rather than assuming every granule marketed for community fish is suitably sized. Variety concerns food type, not larger portions: keep the whole daily offering within the few-minute limit.

Introduce the group to a ready aquarium

Prepare the aquarium before arranging the introduction. Confirm a base of at least 60 × 30 cm or equivalent, establish 23–28°C, pH 5.0–7.0 and 1–8 dGH, and test ammonia and nitrite at zero. Check that the filter is operating normally and that the planned total group contains at least 8–10 Red-Line Tetras.

OATA advises increasing an aquarium's fish population slowly because the beneficial bacteria in a mature filter need to grow as livestock and feeding increase. Apply that principle to the whole stocking plan: do not combine the tetra introduction with several unrelated increases in livestock. The Red-Line Tetras still need their proper social group; gradual stocking refers to the aquarium's total biological load, not keeping one tetra alone.

Follow the arrival sequence

1. Receive the parcel in person and start filming. Begin a continuous video while the parcel is still sealed, before opening it.
2. Open the parcel in the same continuous take. Show the fish inside the sealed bag before anything is disturbed.
3. Float the bag. Float the bag for 20–30 minutes before releasing the fish.
4. Release the fish without adding bag water. Never pour the bag water into the aquarium.

Use clear checkpoints

Respond to a change with measurements. If a fish hangs at the surface, sits on the bottom, swims erratically, breathes differently, hides more, changes colour or stops feeding, test ammonia, nitrite and the other water values promptly. These signs identify the need to investigate; they do not identify one disease or justify a treatment by themselves.

Keep a short record of test results, maintenance and feeding observations through the first month. A sequence of comparable weekly readings shows whether the biological filter is keeping pace more clearly than one isolated result. Delay further stocking if ammonia or nitrite rises above zero.

Keep a socially complete shoal

Plan at least 8–10 Red-Line Tetras together. Seriously Fish gives that recommendation for this animal, while OATA's wider advice says tetras should be kept in groups of at least five and that more is better. Follow the higher 8–10 figure when planning this shoal rather than treating five as the target.

Count the fish before counting other species

A community plan containing four Red-Line Tetras and four unrelated tetras does not create an eight-fish Red-Line Tetra group. Reserve room for at least 8–10 of the same animal first, then assess whether the aquarium can also support another group. Seriously Fish notes that other schooling fish may provide security, but they should be screened as separate residents with their own space, water and social needs.

Observe the group as a whole rather than using stripe intensity as the only measure of welfare. OATA's practical warning signs include changed swimming, darker or paler colour, increased hiding, altered breathing, damaged fins or scales, changing body condition and reduced feeding. Compare behaviour with that group's normal pattern and test the water when a change appears.

Plan the count without assuming a particular sex ratio. The offer does not guarantee male or female fish, and sex should not be inferred from dispatch size, colour or gallery appearance. The dependable customer decision is therefore the total number of fish, supported by enough space and compatible water.

Screen every proposed companion

Red-Line Tetra is described as very peaceful and can suit a well-researched community. Compatibility is conditional rather than universal: every candidate must pass checks for predation risk, temperament, adult size, water overlap, social requirements and total use of the aquarium.

Use the five-part screen

1. Predation: avoid any fish large enough to eat this small tetra.
2. Temperament: favour peaceful residents of a similar size. Treat larger or boisterous species cautiously because they may unsettle smaller fish.
3. Water: require an overlap with 23–28°C, pH 5.0–7.0 and 1–8 dGH rather than matching temperature alone.
4. Space: preserve a base of at least 60 × 30 cm or equivalent for the tetra group and allow for the adult size and activity of every other resident.
5. Social needs: reserve room for at least 8–10 Red-Line Tetras before adding the group requirements of another animal.

Use conditional companion groups

Seriously Fish recommends similarly sized characids, gasteropelecids and lebiasinids, smaller callichthyid or loricariid catfishes, and non-predatory small-to-medium-sized cichlids. These groups remain candidates only when the particular animal is peaceful, cannot eat a 3 cm tetra, shares the complete water range and fits the aquarium's footprint and filtration capacity.

OATA says small tetras should not be kept with fish large enough to eat them and that tetras mix best with animals of similar size and temperament. It also warns that larger or more boisterous fish can be unsuitable for timid or long-finned companions. Use those principles to assess the exact combination rather than treating a family name as a guarantee.

Test a community plan step by step

Write down the proposed residents before deciding that a community is suitable. Record each animal's adult size, temperament, predation risk, temperature, pH, hardness, minimum group and space requirement. Compare the rows rather than relying on a general label such as peaceful or tropical.

Work through common outcomes

A matching temperature is only one part of the water decision. For example, two animals may both tolerate 25°C while one requires pH above 7.0 or hardness above 8 dGH. That combination would not share the full Red-Line Tetra range. Compare all three principal values before moving to temperament and space.

Next, consider the aquarium as a finite footprint. The approximately 54-litre reference and 60 × 30 cm minimum base address the starting point for this tetra; they do not guarantee room for every proposed community. Count the tetra shoal, the full group needs of other social fish and the adult size of each resident. Then check whether the mature filter can maintain zero ammonia and zero nitrite under the planned load.

For a stocking and compatibility assessment, contact us with the aquarium's base dimensions and volume, current temperature, pH, hardness, ammonia, nitrite and nitrate readings, plus the identity, number and adult size of every resident. Those details allow the proposed combination to be screened against the same rules.

Answer Red-Line Tetra buying questions

How big does the Red-Line Tetra get?

FishBase records a maximum length of 3 cm standard length for this peaceful American tetra from Amapá, Brazil.

What size aquarium does Hyphessobrycon amapaensis need?

Use an aquarium with a base of at least 60 × 30 cm or equivalent; Seriously Fish gives approximately 54 litres as the reference volume for that footprint.

How many Red-Line Tetras should I keep?

Seriously Fish recommends at least 8–10 together, so one or two fish do not meet the stated group recommendation for this shoaling tetra.

Is the Red-Line Tetra suitable for beginners?

It suits a keeper who can provide a mature biological filter, weekly testing, a group of at least 8–10 and water within 23–28°C, pH 5.0–7.0 and 1–8 dGH.

What does the Red-Line Tetra eat?

Feed good-quality flake or suitably small granules once daily, add small live, frozen or freeze-dried foods for variety, and limit the portion to what the group eats within a few minutes.

What temperature and pH does it need?

Seriously Fish gives 23–28°C, pH 5.0–7.0 and 1–8 dGH for this fish; OATA's broader tetra guidance also requires zero ammonia, zero nitrite and nitrate no more than 20 mg per litre above the tap-water baseline.

Is this fish aggressive or likely to nip fins?

Seriously Fish describes it as very peaceful, but every proposed companion still needs screening for temperament, predation risk, water requirements and space.

Which kinds of animals can live with it?

Consider similarly sized characids, gasteropelecids or lebiasinids, smaller callichthyid or loricariid catfishes, and non-predatory small-to-medium-sized cichlids only when their water, temperament, space and social needs align; avoid fish large enough to eat it.

How does it arrive alive in the UK?

Tropical Fish Co's policy requires someone to receive the parcel. Film every delivery continuously from the sealed parcel as it is opened, with the fish still visible inside the sealed bag; float the bag for 20–30 minutes, release the fish and never pour the bag water into the aquarium.

Consult the care references

• FishBase species summary: current scientific identity, family, natural distribution, environment and maximum recorded standard length.
• Seriously Fish species profile: aquarium footprint, water range, filtration reference, habitat, diet, behaviour and conditional companion groups.
• OATA tetra and pencilfish guidance: UK group husbandry, testing, maintenance, feeding, introduction and compatibility principles.
• RSPCA aquarium environment guidance: biological filtration and the conversion of ammonia through nitrite to nitrate.
• Tropical Fish Co delivery policy: current dispatch, delivery and Live Arrival Guarantee terms and claim route.