Swordtail Red (Xiphophorus helleri red)

Choose it for a roomy livebearer aquarium

The Swordtail Red (Xiphophorus helleri) is a red ornamental form of a poeciliid livebearer native to North and Central America, from Veracruz in Mexico to north-western Honduras. It reaches 14 cm, so it suits a keeper who can provide a long, mature aquarium, stable water at pH 7.0–8.0 and companionship without crowding. Its combination of active swimming, group needs and aggression between males makes space and stocking more important than its reputation as an undemanding community fish might suggest.

FishBase records a maximum length of 14 cm, freshwater and brackish environments, and adults living mainly in rapidly flowing streams and rivers with abundant vegetation. They also occur in warm springs, weedy canals and ponds. FishBase now lists it as Xiphophorus hellerii. FishBase notes that the red varieties are especially popular aquarium fishes.

Plan the aquarium around 14 cm

Plan for an adult size of 14 cm, even when the fish you receive is much smaller. FishBase records a maximum total length of 14 cm, so base space, filtration and companion choices on that length.

Use an aquarium with a base of at least 120 × 30 cm and a volume of approximately 108 litres. Seriously Fish describes those dimensions, or an equivalent footprint, as the smallest that should be considered. FishBase separately gives a minimum aquarium length of 80 cm; the longer 120 cm footprint allows more useful swimming space and more room for fish to move apart.

Seriously Fish notes that décor is flexible. A heavily planted layout with a dark substrate can show the fish clearly, while floating plants and driftwood roots or branches diffuse the light and add a more natural feel. Keep a substantial open route through the aquarium because OATA particularly highlights open swimming space for swordtails.

Understand the fish and size you are choosing

One purchase supplies one Swordtail Red from the size selected on the live size selector. The labelled dispatch sizes are 3 - 4 cm, 4 - 5 cm, 5 - 6 cm and 7 - 8 cm. These labels describe the fish’s size when supplied and do not change the 14 cm adult planning figure. The size you select is the size supplied, not the adult size.

Sex is guaranteed only when the selected option explicitly states male or female. This Swordtail Red listing has no sex-guaranteed option. Do not use a dispatch measurement, body colour or gallery fin shape to predict the sex of the animal supplied. Plan enough space for the group to be managed after the fish develop clear individual characteristics.

The gallery images are representative, based on reference photographs of this species, so colours can look slightly different from the live animal. The images illustrate the red-orange form and swordtail body shape, but the number of fish shown in a scene does not alter the purchase unit of one animal.

Use the selector for the preferred dispatch size, then plan the aquarium around the adult fish. Smaller arrivals do not make a smaller permanent aquarium suitable, and a larger dispatch fish still needs a careful introduction to the same stable conditions. You can also browse the livebearers collection when comparing this fish with other members of the group.

Build the aquarium before the fish arrives

Prepare a mature, filtered aquarium with a base of at least 120 × 30 cm and approximately 108 litres of water. Use a larger aquarium when the swordtail group, other residents or décor reduce the usable swimming space. The footprint provides active fish with useful swimming room.

A keeper new to the hobby can manage this fish when prepared to provide the full aquarium footprint, test the water and manage the social group rather than choosing by colour alone. OATA describes most platies and swordtails as easy to keep, but this larger swordtail still needs a properly established biological filter, open swimming room and attention to male behaviour.

Divide the layout into useful zones

• Open swimming route: keep a clear path through the aquarium rather than filling every part with ornaments.
• Planted cover: use live plants where practical, or suitable artificial plants and ornaments that create shelter.
• Sheltered areas: place plants, wood or branches around the open swimming route so fish can use both cover and open space.
• Stable base: give the aquarium gravel or sand, and siphon solid waste from it during maintenance.

Seriously Fish says filtration need not be especially strong, although the fish appears to appreciate some water movement. Arrange the outlet so it circulates water without turning the full swimming route into a forceful current. A flowing section and a calmer planted section let the fish choose where to spend time.

Mature the biological filter before adding livestock. The filter bacteria must be able to process ammonia into nitrite and then nitrate, and the population must expand when more fish and food are added. Add fish gradually rather than making a large change to the biological load in one step. Our first tropical aquarium guide explains how to prepare and mature the system before livestock arrives.

Check the final usable volume after substrate and décor have been added. A nominal aquarium volume is not the same as the water actually present, while a tank with the correct volume but a short footprint may still lack the swimming length recommended for this species.

Keep the water at 22–27°C, pH 7.0–8.0 and 10–12 dGH

Keep the aquarium at 22–27°C, pH 7.0–8.0 and 10–12 dGH. These values fall within all three published ranges: FishBase records 22–28°C, pH 7.0–8.0 and 9–19 dH in the species’ environment; Seriously Fish gives 16–28°C, pH 7.0–8.0 and 10–25 dGH for aquarium care; and OATA’s swordtail group guidance gives 22–27°C, pH 7.0–8.0 and 4–12 dGH. Aim for water that meets all three at once: 22–27°C, pH 7.0–8.0 and 10–12 dGH.

Test before changing anything

Measure the source water and mature aquarium before choosing an adjustment. Do not soften, harden, acidify or alkalise the water unless a test shows it is outside the target range. The useful decision is whether the measured aquarium sits within the target and remains stable. Our water chemistry guide explains the values to measure, while the water matcher helps compare those measurements with the stated range.

OATA sets ammonia and nitrite at zero and says nitrate should not exceed 20 mg per litre above the normal tap-water level. Test at least weekly and after any event that may affect the biological filter. Stability within the range is more useful than repeated chemical adjustments that cause abrupt swings.

Match filtration to the aquarium and biological load

Use a well-established biological filter and keep ammonia and nitrite at 0 mg/l. The RSPCA explains that fish release toxic ammonia, which filter bacteria convert first to nitrite and then to safer nitrate. A filter is therefore essential even when the water looks clear.

For an aquarium of approximately 108 litres, Seriously Fish gives a turnover of four to five times the aquarium volume each hour and a filter rating of about 430–540 litres per hour. Treat the rating as a starting point: clogged media, pipework and the aquarium layout can reduce actual flow. Check that water circulates throughout the aquarium while leaving fish able to hold position and rest.

Use a repeatable weekly routine

1. Test ammonia, nitrite and nitrate before the water change so the results show how the aquarium has performed.
2. Change 25% of the water at least once every week, as OATA strongly recommends.
3. Treat replacement tap water with conditioner to remove chlorine or chloramine before it enters the aquarium.
4. Use a siphon to remove solid waste from accessible areas of gravel or sand.
5. Check the filter intake and outlet for blockages and confirm that normal circulation has returned.

Rinse filter media in water removed from the aquarium, never under the tap.

Increase stocking slowly. More fish and more feeding create more waste, but bacterial capacity does not expand instantly. Test after additions and delay further changes if ammonia or nitrite appears. This protects the whole aquarium from the imbalance OATA calls new tank syndrome.

Feed a balanced omnivore diet once a day

Feed once a day, offering only what the fish can eat within a few minutes, as OATA advises for platies and swordtails. Remove or reduce food when portions remain uneaten, because decomposing food adds waste and increases the pressure on the biological filter. Judge the portion by what the whole group actually consumes rather than by a fixed pinch.

Expect an omnivore rather than a specialist feeder. Wild fish eat worms, crustaceans, insects and plant matter, while aquarium guidance adds quality dried food and small live or frozen foods. Give it that variety every week rather than relying on a single food.

FishBase records wild swordtails eating worms, crustaceans, insects and plant matter. Seriously Fish adds aquatic and terrestrial invertebrates, organic detritus, algae and other plant material, identifying the fish as a generalised omnivore. Build the aquarium diet around a good-quality dried food, then rotate small live, frozen or freeze-dried items for variety.

Build the menu

• Regular dried food: use a quality flake or suitably sized granule; OATA recommends one with a high algae content for platies and swordtails.
• Animal-food variety: offer small Daphnia, Artemia, bloodworm or tubifex in forms appropriate to the fish.
• Plant contribution: retain algae and other plant ingredients within the balanced diet instead of feeding only animal foods.
• Portion control: stop when the fish have eaten the offered food within a few minutes.

Match particle size to the mouth of the dispatch-sized fish. A smaller arrival may need flakes broken into manageable pieces or a suitably small granule, while larger individuals can take larger pieces. The nutritional pattern remains the same as the fish grows.

If one fish hangs back, spread a modest portion across more than one point so dominant individuals cannot intercept every item. Continue to keep the total meal within the few-minute limit. A sudden loss of appetite is a health or water-quality warning, not a reason to keep adding different foods throughout the day.

Keep a group with room to separate

Keep at least three swordtails. OATA says platies and swordtails require some companionship and suggests keeping at least three together, two females to each male, to reduce stress on females and other aquarium inhabitants. More may be kept in the same ratio when the aquarium has enough volume, swimming space, filtration and cover for the larger group.

Because this offer does not guarantee sex, build the aquarium around the number of fish and the behaviour that develops rather than assuming a ratio from dispatch size, colour or gallery appearance. Assess the actual group as individual characteristics become clear. If the balance produces persistent pressure on one fish, the solution may require more space, a different group arrangement or separation.

Distinguish display from conflict

FishBase records that males are aggressive towards each other. Seriously Fish adds that groups of males in confined spaces tend to form dominance hierarchies and may spend a significant proportion of their time maintaining their positions. Brief displays can occur, but persistent pursuit, blocked access to food or a fish forced into one corner indicates that the layout or social arrangement needs attention.

Do not solve rivalry simply by adding fish to the same confined space. Extra fish increase the biological load and may create more interactions. Check the 120 × 30 cm minimum footprint, usable cover, water results and filtration before deciding whether the aquarium can support a larger group.

Follow the arrival and acclimatisation procedure

Arrange for someone to receive the parcel because live fish must not be left unattended. Tropical Fish Co hand-packs fish in pure oxygen inside an insulated polystyrene box and uses a heat pack when the weather calls for it. The parcel travels with a licensed live-animal courier, and tracking plus the confirmed delivery date are sent by email.

Follow the delivery-policy steps

1. Start filming every delivery before the parcel is opened. Show the parcel still sealed with the outer box visible, film it being opened in one continuous take and show the fish still inside the sealed bag.
2. Open and inspect the parcel the same day it arrives.
3. Float the bag for 20–30 minutes before releasing the fish.
4. Release the fish without pouring the bag water into the aquarium.

These steps come from the current delivery and Live Arrival Guarantee policy. Read that page before the delivery date so someone can be present. Separately, prepare the aquarium at the FishBase, Seriously Fish and OATA overlap of 22–27°C, pH 7.0–8.0 and 10–12 dGH.

OATA advises increasing the number of fish only slowly, because the filter bacteria must grow each time more fish are added. Test ammonia and nitrite after introduction because the mature filter must respond to the additional waste and feeding. Add further livestock only after readings remain at zero and the existing residents are feeding and behaving normally.

A dispatch-sized fish still needs the adult aquarium footprint from its first day. Moving a small fish into a temporary undersized aquarium creates another transfer later and does not reduce its need for stable filtration, appropriate water and companionship.

Respond to changes before they become severe

Observe swimming, breathing, colour, appetite, body condition and social position every day. You are looking for change from that individual fish’s normal pattern rather than a single ideal pose. OATA highlights hanging at the surface, sitting on the bottom, erratic swimming, unusual hiding, altered aggression, faster or slower gill movement, colour change, white spots, fluffy growths, damaged fins or scales, weight change and reduced feeding as warning signs.

Use a simple response order

1. Test first: measure ammonia, nitrite, nitrate, temperature and pH as soon as behaviour or appearance changes.
2. Check equipment: confirm the heater, filter flow and water circulation are operating normally.
3. Review recent changes: consider new fish, increased feeding, filter cleaning or an interrupted maintenance routine.
4. Reduce immediate pressure: separate a fish when persistent aggression is causing injury or preventing feeding.
5. Record the pattern: note when the change began, the test results and which fish are affected.

If you are concerned about a health change, test the water quality first and write down exactly what the behaviour or appearance shows. Do not choose a disease treatment solely from one visible sign, because poor water quality and social pressure can produce overlapping symptoms.

Keep changing 25% of the water at least once every week and testing at least weekly. Consistent results are more informative than a single clear test taken immediately after a water change. A stable aquarium should keep ammonia and nitrite at zero while the fish maintain appetite, body condition and normal access to the group’s swimming and feeding areas.

Screen every community combination before adding fish

Treat Swordtail Red as generally peaceful, but do not treat that description as a universal tank-mate list. OATA says platies and swordtails are generally compatible with other species, while warning that large swordtails can be boisterous and may chase more timid tank mates. FishBase records that males are aggressive towards each other, and Seriously Fish adds that males kept in confined spaces tend to form dominance hierarchies.

Apply three checks

1. Water: choose animals whose routine requirements overlap 22–27°C, pH 7.0–8.0 and 10–12 dGH.
2. Space: calculate the adult space and biological load of the whole community, not only the swordtails.
3. Behaviour: allow for active swimming, male rivalry and the possibility that a larger swordtail may chase a timid neighbour.

A candidate that passes only one or two checks is not a sound match. A peaceful fish whose water requires a different pH or hardness creates conflicting care. A water-compatible fish may still be too timid for persistent activity. A suitable temperament can also fail when the aquarium lacks enough length, cover or filtration for the combined adult stock.

Before adding any tank mate, list the aquarium dimensions, measured water values, filtration and the number and adult size of every resident, and go ahead only when the newcomer passes all three checks. Add companions gradually and watch how every resident feeds and moves after each addition.

Manage behaviour after every introduction

Judge compatibility by what happens after fish share the aquarium. Watch whether each animal can feed, rest and move through the layout without being continually pursued. A combination that appears calm at first can change as the fish settle, grow or establish positions within the group.

Use behaviour to choose the next action

• All fish feed and separate normally: maintain the established layout and weekly routine.
• One swordtail patrols the whole aquarium: increase planted cover and shelter, then check whether the footprint provides meaningful separation.
• A timid resident stays hidden: determine whether chasing is preventing normal movement or feeding.
• Male rivalry becomes persistent: review the group arrangement instead of adding more fish automatically.
• Fins or scales become damaged: separate the affected fish and test the water immediately.

Do not confuse activity with harmlessness. OATA describes the group as generally peaceful but also says large swordtails may be boisterous. FishBase directly records aggression between males, and Seriously Fish explains that confined male groups may spend considerable time maintaining dominance. The aquarium should provide open swimming room as well as plants and shelter.

Recheck compatibility as fish approach 14 cm. Dispatch measurements represent the fish at supply, while adult body size changes swimming space and waste production. A community that is comfortable with smaller individuals can become crowded as several residents grow.

When considering another addition, use the adult measurements of all residents and confirm ammonia and nitrite remain at zero. Additions should be gradual because filtration bacteria need time to adjust to more waste and feeding. If the existing group is already using all open space or showing persistent social pressure, improve that situation before increasing the stock.

Get answers to common Swordtail Red questions

How big does it get?

Swordtail Red reaches 14 cm; FishBase records this maximum length, so plan the aquarium around 14 cm rather than the dispatch measurement.

What size aquarium does it need?

Swordtail Red needs an aquarium with a base of at least 120 × 30 cm and a volume of approximately 108 litres; Seriously Fish describes that footprint or an equivalent as the smallest that should be considered.

How many should I keep together?

OATA recommends keeping at least three Swordtail Red and suggests two females to each male, but this offer does not guarantee sex, so provide enough space to manage the group that develops.

Does it suit beginners?

OATA describes most platies and swordtails as undemanding and easy to keep, so a keeper new to the hobby can manage Swordtail Red in a mature, filtered aquarium large enough for a group.

What does it eat?

Swordtail Red is an omnivore that eats invertebrates and plant matter; feed a quality flake or granule with a high algae content once daily, adding small Daphnia, Artemia, bloodworm or tubifex for variety and limiting the portion to what is eaten within a few minutes.

What temperature and pH does this fish need?

Keep it at 22–27°C, pH 7.0–8.0 and 10–12 dGH; this is the overlap of FishBase’s recorded environment, Seriously Fish aquarium care and OATA’s swordtail guidance.

Is it aggressive or likely to nip fins?

Males are aggressive towards each other, and groups of males in confined spaces tend to form dominance hierarchies; watch for persistent chasing, fin damage or a fish being excluded, then review the available space, cover and group arrangement and separate fish when pressure continues.

Which kinds of fish or invertebrates can live with it?

Choose generally peaceful animals whose needs overlap 22–27°C, pH 7.0–8.0 and 10–12 dGH, then check adult space and behaviour because OATA warns that large swordtails may chase more timid tank mates.

How does it arrive alive in the UK?

Film the sealed parcel before opening it, as one continuous unboxing video for every delivery. This fish is hand-bagged in pure oxygen, packed in an insulated polystyrene box with a heat pack when needed and carried by a licensed live-animal courier; someone must receive it, then float the bag for 20–30 minutes before release without pouring bag water into the aquarium.

Check the care and identity references

• FishBase: accepted species name, family, native range, recorded environment, maximum length, habitat, diet and male aggression.
• Seriously Fish: aquarium footprint, approximate volume, water ranges, filtration, décor, feeding and dominance behaviour.
• OATA: UK group care for platies and swordtails, including companionship, feeding, maintenance, water quality and health observations.
• RSPCA: general aquarium-welfare guidance on biological filtration and nitrogenous waste.
• Tropical Fish Co delivery policy: packing, receipt, acclimatisation and Live Arrival Guarantee claim procedure.