Glass Bloodfin Tetra (Prionobrama filigera)

Decide if this active tetra suits your aquarium

The Glass Bloodfin Tetra (Prionobrama filigera) is a freshwater characin from the Amazon River basin in South America. FishBase places it in the tetra family Characidae and records a maximum length of 6 cm. It is a generally peaceful, active, open-water fish for keepers who can provide a mature filtered aquarium, a proper group and uninterrupted swimming room.

Seriously Fish describes it as an excellent choice for beginners because it is relatively unfussy about water chemistry, food and companions. That suitability still depends on meeting its group, space and water-quality needs from the start. It is not a fish for a bowl, an unfiltered aquarium or a plan based on keeping a single specimen.

Plan for its movement, not just its length

Although 6 cm is modest, this species is active and pelagic. It usually uses the upper water layers, so horizontal room and an unobstructed route matter more than decorative height. A group also needs enough surface access for feeding without being crowded by faster fish.

Choose it when you want a social tetra whose behaviour is central to the display. The practical commitment is a complete group, stable tropical conditions and space arranged around regular movement rather than a single feature fish.

Choose the dispatch size with the adult plan ready

One purchase supplies one Glass Bloodfin Tetra in the size selected. Use the live size selector to choose from the labels 2-3 cm, > 4.5 and 3.5 cm. The size you select is the size supplied, not the adult size. Every fish therefore needs the same adult aquarium plan regardless of its dispatch label.

A smaller dispatch fish is not a reason to begin with a smaller aquarium. Prepare the full footprint, filtration, group capacity and compatible community before arrival. Planning this way avoids moving the fish simply because it grows towards the recorded 6 cm adult length.

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

The gallery images are representative, based on reference photographs of this species, so colours can look slightly different from the live animal.

Build the full group into the budget and stocking plan

The fish are sold individually, while the species should be kept in groups of at least 6–8. A group of eight meets that recommendation and gives a clear starting number when calculating aquarium capacity. More can be considered only when the aquarium has suitable space, filtration and total stocking capacity.

Use the selector for the supplied size and quantity, then judge the aquarium by the adult group. If you are comparing related fish before making that decision, browse our tetras collection and compare adult size, group needs, swimming zone and water requirements rather than colour alone.

Use one clear set of planning numbers

Keep the aquarium at 23–27°C, pH 6.5–7.5 and 4–12 dGH for a practical routine target. The temperature and pH are the overlap of FishBase, Seriously Fish and OATA’s tetra guidance; the hardness target is the overlap of Seriously Fish and OATA. OATA’s figures are group guidance, not a species-specific optimum.

Seriously Fish says a 60 × 38 cm base with a volume of about 68 litres is just about acceptable for a small group. Because this species reaches more than 5 cm, OATA’s broader tetra guidance recommends at least 80 litres for the larger size category. Plan around 80 litres or more where possible while treating the 60 × 38 cm base as a firm footprint reference.

Use stability as the final test

Numbers describe the operating range, but stability decides whether the plan works. Confirm the aquarium can maintain the chosen temperature and chemistry before adding the group. Match companions to the same range, leave capacity for their combined waste and avoid repeated changes made simply to chase a particular point within the range.

Build an open upper-water swimming route

Arrange the aquarium around a long, open route through the upper water layers. Seriously Fish describes this active species as pelagic and usually found in the upper water layers in nature, and says the aquarium should contain plenty of open space for swimming. Plants and wood should frame that route rather than divide it into narrow gaps.

Start with the footprint

Use a base of at least 60 × 38 cm. About 68 litres is just about acceptable for a small group, while 80 litres or more gives a more practical margin for a group of at least 6–8 fish that each reach 6 cm. Additional volume is useful only when the shape still provides horizontal swimming room.

A tall, narrow aquarium can hold a similar volume while giving less useful movement space. Check the base dimensions as well as the litre figure, and keep the upper-front or upper-centre area clear from end to end. Place tall plants where they offer cover without blocking that route.

Use plants to provide cover and calm the group

A well-planted aquarium with patches of floating plants suits this species. Surface vegetation will help calm fish that become skittish, especially when they are first introduced, but it should not cover the entire surface. Leave clear areas where the group can reach food and where water can move freely.

Driftwood twigs and leaf litter can be used to create a natural-looking lower area. Keep wood stable, use aquarium-safe materials and make sure decorative branches do not project into the main swimming lane. Plants around the sides and rear preserve cover while allowing the group to move together.

Check the layout from the fish’s route

• Trace an unobstructed horizontal path through the upper water.
• Keep part of the surface open for feeding.
• Use planted margins and floating cover without sealing the surface.
• Secure wood and ornaments so the group cannot be channelled into tight spaces.
• Leave access around the filter intake and outlet for inspection and cleaning.

Review the route after plants grow. A layout that begins open can become crowded, so trim vegetation before it removes the swimming space on which the original aquarium plan was based.

Establish the filter before adding the group

Use a mature biological filter before adding Glass Bloodfin Tetras. The RSPCA explains that aquarium filters provide a home for beneficial bacteria that process toxic ammonia into nitrite and then into the safer nitrate. A running filter is not enough by itself; the bacterial population must be established and capable of handling the aquarium’s livestock and feeding load.

If this is your first aquarium, follow our first tropical tank preparation guide before arranging an arrival. Confirm that the heater, filter and test routine work consistently in the completed aquarium rather than testing equipment for the first time with fish present.

Prepare for the whole social group

This species needs at least 6–8 together, so account for the waste produced by the planned group. OATA advises increasing aquarium populations slowly because beneficial bacteria need to respond as fish numbers and feeding increase. If other livestock already live in the aquarium, assess the combined load before adding another complete group.

Do not solve limited biological capacity by planning to keep one Glass Bloodfin Tetra alone. Instead, improve the aquarium plan before purchase: provide sufficient mature filtration, reduce other stocking where appropriate or choose a larger established aquarium that can receive the required group.

Confirm the filter is doing its job

• Ammonia must read zero mg per litre.
• Nitrite must read zero mg per litre.
• The filter must run continuously and remain free of blockages.
• Flow must circulate the aquarium without removing the group’s usable swimming space.
• The aquarium must hold its intended temperature throughout the normal daily cycle.

A clear aquarium is not automatically a biologically safe aquarium. Ammonia and nitrite are invisible, so use suitable tests rather than appearance as the test of readiness. Delay adding fish when either reading is above zero.

Keep enough access around the filter to inspect it without dismantling the aquascape. Early recognition of reduced flow or a blocked intake is easier and safer than waiting for water quality to deteriorate.

Keep water values stable and test them weekly

Maintain 23–27°C, pH 6.5–7.5 and 4–12 dGH as the routine target. These are practical overlap values: FishBase, Seriously Fish and OATA overlap on the temperature and pH target, while Seriously Fish and OATA overlap at 4–12 dGH. Choose a stable point within those ranges rather than allowing values to move repeatedly between their limits.

Use our water chemistry guide to understand what each test measures, then compare your readings with the target through the aquarium water matcher. Test the actual aquarium and the replacement water used during maintenance; assumptions based only on local tap-water reputation can miss changes within a home or supply area.

Apply the weekly maintenance routine

At least once every week, make a partial water change of 25%. Follow this schedule consistently to remove accumulated waste and support stable water quality. Use a siphon to remove solid waste from accessible gravel or sand while preserving the planted cover and open swimming layout.

Treat replacement tap water with a conditioner that removes chlorine or chloramine before adding it to the aquarium. Bring the replacement water into a suitable condition for the aquarium and avoid a sudden temperature or chemistry shift during the change.

Use the test results to decide what to do

OATA advises keeping nitrate no more than 20 mg per litre above the normal tap-water level. Record both figures so the aquarium reading is interpreted against its actual starting point rather than against an isolated number.

Clean the filter without damaging its bacteria

Check the filter for blockages. When the media needs cleaning, do not run it under the tap. Rinse it lightly in aquarium water removed during a partial water change, which reduces the loss of its beneficial bacterial population.

Match flow and heating to the aquarium

Choose equipment from the completed aquarium’s real volume, shape and room conditions. For the Seriously Fish reference aquarium of about 68 litres, a turnover of four to five times the aquarium volume per hour corresponds to a filter rating of about 270–340 litres per hour. Treat that as a starting equipment calculation, then check how the filter performs after media, plants and décor are in place.

Preserve swimming space while circulating the water

Position the outlet so water moves throughout the aquarium without forcing the group into one sheltered corner. The upper-water route should remain usable in both directions. If the fish continually struggle against one concentrated jet, redirect or diffuse that jet while maintaining circulation through the rest of the system.

Do not judge filtration only from the printed flow rating. Media, pipework and blockages can reduce output, while an outlet aimed through a narrow gap may create a locally forceful current. Check movement across the whole aquarium and inspect the filter whenever its normal sound, output or surface movement changes.

Size the heater for the room as well as the volume

Seriously Fish estimates roughly 75–100 W to hold 23–27°C in an aquarium of about 68 litres when the room is around 20°C. That example is a planning calculation, not a reason to ignore the manufacturer’s aquarium-volume guidance or the temperature of the room in which the aquarium stands.

Use a separate aquarium thermometer to confirm the result. Place it where it represents the main water body rather than directly beside the heater. Check the reading at different points in the normal household routine until you know that the aquarium remains within 23–27°C.

Make equipment checks routine

• Confirm the filter is running and the outlet flow looks normal each day.
• Read the thermometer rather than relying on the heater dial.
• Inspect intakes for leaves and debris.
• Check that floating plants have not collected around the outlet or sealed the surface.
• Investigate a changed sound, reduced flow or unexpected temperature before it becomes a water-quality problem.

Stable equipment supports stable water. Keep spare test supplies and water conditioner ready for routine maintenance, and arrange cables and access so the filter and heater can be inspected without disturbing the group or dismantling the aquarium.

Feed small invertebrate-based foods at the surface

Feed a varied diet that reflects this species' natural feeding on small invertebrates. Seriously Fish links the upturned mouth and slightly keeled body to feeding primarily on small invertebrates taken from the water surface in the wild. In the aquarium, it particularly favours live and frozen Daphnia, bloodworm and Cyclops, while most specimens also accept suitable dried foods.

Use a quality dried food of an appropriate particle size as the regular prepared component, then rotate Daphnia, small bloodworm or Cyclops for variety. OATA’s tetra guidance also supports quality flake or granules with small live or frozen foods. Every item must be small enough for the fish to take promptly.

Use one controlled daily feed

Feed once a day and offer only what the group can eat within a few minutes. This schedule follows OATA’s portion guidance and gives a clear limit for adjusting quantity. Activity at the surface is not a reason to continue adding food after the planned portion has been eaten.

Place food where the fish naturally feed, then watch whether the whole group reaches it. Avoid releasing one large clump in a single point. Several small placements across the open feeding area can reduce crowding while still keeping the total portion within the few-minute limit.

Let the aquarium tell you when the portion is wrong

Overfeeding allows uneaten food to break down and release waste into the water. It also increases the load on the biological filter. Adjust the next feed rather than adding compensating products to an aquarium receiving too much food.

Variety means rotating suitable foods, not increasing the total amount. Keep the once-daily schedule and use observation to refine the portion for the actual number of fish in the aquarium.

Watch the group through the first month

Observe the whole group at the same time each day, especially after introduction. Surface vegetation will help calm Glass Bloodfin Tetras, which can occasionally be a little skittish when first added. Give them planted cover and an open route rather than reacting to initial caution by making repeated changes to the aquarium.

Use the first week to confirm basic function

• Check that every fish can use the upper-water swimming route.
• Watch the group feed and confirm that no individual is repeatedly excluded.
• Test ammonia and nitrite and keep both at zero mg per litre.
• Confirm that temperature remains within 23–27°C.
• Look for clear eyes, intact scales and undamaged fins.

OATA advises watching swimming behaviour, colour, temperament, breathing, appearance, body condition and feeding. Changes become more useful when compared with the fish’s normal pattern, so keep brief notes during the first week rather than relying on memory after a problem develops.

Use the first month to confirm the stocking plan

Watch whether the group has enough room to move without continual competition from other upper-water fish. Check that all companions share the routine temperature and pH range and that feeding remains accessible. Review the aquarium after plants settle and trim growth that begins to block the planned route.

Continue weekly testing even when the aquarium looks clear. Beneficial bacteria must respond to the additional waste and feeding associated with the new group. A stable first few days do not replace the weekly ammonia, nitrite and nitrate routine.

Match a change to the first useful action

Do not treat every brief movement as a problem. Look for a change from the group’s normal pattern, then use test results and direct observation to decide the next step.

Follow the arrival steps in the right order

Prepare the mature aquarium, confirm its water values and make sure someone is in to receive the parcel, because live fish must not be left unattended. Fish are packed in pure oxygen inside an insulated box, with a heat pack used when the weather calls for it. Read our delivery and Live Arrival Guarantee policy before the arrival day.

Use this arrival sequence

1. Start filming while the parcel is still sealed and the outer box is visible.
2. Open it in one continuous take and show the fish inside the sealed bag before anything is disturbed.
3. Inspect the fish on the same day the parcel arrives.
4. Float the bag for 20–30 minutes before releasing the fish.
5. Release the fish without pouring the bag water into the aquarium.

For a Live Arrival Guarantee claim, contact us on the same day with the order number and continuous unboxing video showing the sealed parcel, the opening and the fish inside the sealed bag.

Return to the prepared care plan after release

Give the group access to the open upper-water route and planted cover already arranged for it. Surface vegetation will help calm newly introduced fish. Avoid rearranging the whole aquarium in response to temporary caution; first confirm temperature, ammonia, nitrite and the behaviour of existing companions.

Watch feeding access and swimming during the settling period. If a fish behaves differently from the rest of the group, test the water before making assumptions. Keep ammonia and nitrite at zero mg per litre and verify that the temperature remains within 23–27°C.

The arrival process works best when every aquarium decision has already been made: the filter is mature, the full social group has been planned, companions have been screened and the final adult footprint is in place.

Screen every companion for space and feeding competition

Choose peaceful fish that enjoy 23–27°C, pH 6.5–7.5 and a compatible hardness, then compare adult size, swimming zone, activity and feeding speed. Glass Bloodfin Tetras are generally peaceable, but compatibility depends on the aquarium giving every species enough room and reliable access to food.

Suitable candidates named for this species

Seriously Fish names similarly sized characins, Corydoras, smaller Loricariid catfish, Apistogramma and Mikrogeophagus as suitable companions. In a suitably sized aquarium, Seriously Fish also names slightly larger cichlids such as angelfish or discus as good companions. Each name is a candidate for screening, not a reason to ignore the companion’s own group, footprint or water needs.

Keep bigger, fast-swimming fish out of the plan

Avoid bigger, fast-swimming species that inhabit the same area of the aquarium. Seriously Fish warns that Glass Bloodfin Tetras do not do well when competition for space and food is fierce. A bigger, fast-swimming fish sharing the upper water still competes for space and food, so choose a different companion.

OATA’s broader tetra advice favours species of a similar size and temperament. Use that as the first screening filter, then leave out any bigger, fast-swimming fish that use the same area.

Test the complete community plan

• Compare every species at its adult size.
• Add the full group requirements, not one example fish from each species.
• Map which fish use the upper, middle and lower areas.
• Check that every species shares the proposed temperature and chemistry.
• Confirm the filter can support the combined stocking and feeding load.
• Leave a clear feeding area for the surface-feeding tetra group.

If any one of these checks fails, change the companion or the aquarium plan before mixing the fish.

Manage group behaviour with space and numbers

Keep at least 6–8 Glass Bloodfin Tetras together. Seriously Fish says the species should always be maintained in a group of at least 6–8, while OATA warns that tetras kept singly or in groups that are too small often become stressed. More can be considered when the aquarium has the footprint, filtration and total capacity to support them.

Separate ordinary interaction from a welfare warning

Rival males may sometimes squabble among themselves. When squabbles happen, judge whether all fish continue to swim, feed and use cover normally.

Persistent hiding, reduced food intake, damaged fins, altered colour, abnormal breathing or a fish repeatedly separated from the group should prompt a water test and a review of space and companions. Those signs require action even when the community was peaceful previously.

Protect access to food

The upturned mouth and surface-feeding biology make the upper feeding area important. A companion can share the same water values yet still be unsuitable if it reaches every portion first. Watch a complete feed rather than assuming that food added to the aquarium is food eaten by every fish.

Use more than one surface placement for the same controlled portion. If faster companions continue to dominate, change the community plan rather than increasing food until uneaten material pollutes the aquarium.

Reassess as the community develops

Compatibility is an ongoing condition. Recheck adult size, swimming space and feeding competition as fish grow and plants fill the layout. Preserve the open route and stable water values that made the original combination workable.

Answer the main Glass Bloodfin questions

How big does a Glass Bloodfin Tetra get?

It reaches 6 cm. FishBase records 6 cm total length, so plan the aquarium and community around that adult figure rather than the selected dispatch size.

What size aquarium does a Glass Bloodfin Tetra need?

Plan 80 litres or more. Seriously Fish says a 60 × 38 cm base and about 68 litres is just about acceptable for a small group, while OATA recommends at least 80 litres for tetra species over 5 cm.

How many Glass Bloodfin Tetras should I keep together?

Keep at least 6–8 together. Seriously Fish gives that minimum for this species, and OATA warns that tetras kept singly or in groups that are too small often become stressed.

Is the Glass Bloodfin Tetra suitable for beginners?

Yes. Seriously Fish describes it as an excellent beginner choice because it is relatively unfussy about water chemistry, food and companions. Have its mature filtered aquarium, full group and swimming space ready before it arrives.

What does a Glass Bloodfin Tetra eat?

Feed it suitable quality dried food with small live or frozen Daphnia, bloodworm and Cyclops. Seriously Fish links its upturned mouth to taking small invertebrates from the surface; OATA advises one portion daily, eaten within a few minutes.

What temperature, pH and hardness does it need?

Keep 23–27°C and pH 6.5–7.5, the overlap of FishBase, Seriously Fish and OATA; keep hardness at 4–12 dGH, the overlap of Seriously Fish and OATA. Hold these values stable.

Is it aggressive or likely to nip fins?

It is generally peaceable, although rival males may sometimes squabble. Persistent fin damage, hiding, feeding loss or unusual aggression is a reason to test the water and reassess group size, space and companions.

Which fish can it live with?

It makes an excellent companion for similarly sized characins, Corydoras, smaller Loricariid catfish, Apistogramma and Mikrogeophagus. Angelfish or discus require a suitably sized aquarium. Avoid bigger, fast-swimming species using the same area.

How does this fish arrive alive in the UK?

Start filming the sealed parcel before opening it, continue through the opening and show the fish inside the sealed bag. Fish are hand-bagged in pure oxygen and packed in an insulated poly box, with a heat pack when the weather calls for it. Someone must be in to receive the parcel, because live fish must not be left unattended; inspect the fish the same day and float the bag for 20–30 minutes before releasing them.

Check the public care references

• FishBase: Prionobrama filigera — identity, family, Amazon distribution, recorded adult length and environmental range.
• Seriously Fish: Prionobrama filigera — aquarium footprint, water, habitat layout, diet, behaviour and named companion guidance.
• OATA: tetras and pencilfish — group care, feeding, water quality, maintenance and health observations.
• RSPCA aquarium environment advice — biological filtration and aquarium waste processing.