Berlin Swordtail (Xiphophorus hellerii)

Berlin Swordtail (Xiphophorus hellerii) is an active livebearing freshwater fish recognised in the aquarium trade for its red-to-orange base colour and irregular black spotting. Every individual develops its own balance of colour and pattern, so the attraction is variation rather than a fixed design. A settled fish brings movement to the middle and upper levels of a suitably spacious aquarium, while planted edges and open swimming room show the body shape well.

This listing was previously described mainly as a Red Marble Swordtail. That wording can describe the broken red-and-black effect, but Berlin Swordtail is the supplier's actual trade identity and is the clearer primary name. Berlin is a cultivated aquarium form, not a separate scientific species. The accepted species name is Xiphophorus hellerii; the supplier has not provided breeder or lineage records, so no exact historic bloodline or country of breeding is promised.

Sale unit: one selected quantity is one unsexed fish in the chosen live size option. It is not a pair or trio. Colour coverage, black spotting, sex, sword length and fin shape vary, and the gallery is representative artwork rather than photographs of the exact fish dispatched. Before ordering, plan an aquarium of at least 80 litres and at least 80 cm long, with more room for a group or mixed community. Browse the wider livebearer collection only after comparing each species' adult size and water needs.

Berlin Swordtail Quick Care Guide

Correct Identity and the Berlin Name

The valid species name is Xiphophorus hellerii, a member of the livebearing family Poeciliidae. The extra second letter i in hellerii matters: current taxonomic catalogues use that spelling even though shortened or older forms appear in trade data. A product title does not need to repeat every supplier phrase to be findable. Using one accurate common name and one accepted scientific name gives customers and search engines a cleaner entity to understand.

Berlin Swordtail is a long-established aquarium trade name. Historical aquarium literature describes a red fish with variable black spotting developed through old swordtail and platy breeding work, followed by backcrossing towards swordtail form. That history helps explain why different Berlin fish can show very different amounts and shapes of black. It does not prove that a modern wholesale shipment comes from one documented heritage line. This page therefore treats the history as context, not as a pedigree certificate.

The old phrase Red Marble is not being hidden. It explains why earlier content and image filenames used that wording, and some keepers may still recognise it. However, marble is a visual description rather than the strongest identity for this stock. It also attracted completely unrelated searches about stone, flooring and kitchens. Removing those forced phrases makes the page more useful without weakening the real aquarium keywords: Berlin Swordtail, swordtail fish, Xiphophorus hellerii, livebearer care and UK availability.

Berlin and Wien Are Different Listings

Berlin and Wien are separate swordtail trade forms in this catalogue. Search engines currently have evidence of the Wien page appearing for a Berlin query, so this distinction needs to be explicit rather than implied. Choose Berlin when the red-to-orange body with irregular dark spotting shown in this representative gallery is the form you intend to order. Use the separate Swordtail Wien listing when that named form is the one you are comparing.

Neither city name changes the basic species-level need for swimming length, mineral-bearing water, mature filtration and sensible social planning. The distinction is primarily a cultivated appearance and trade identity. Do not assume that two products with city names are interchangeable, that they form a guaranteed breeding pair, or that offspring will reproduce a parent pattern predictably. If preserving a named line matters, obtain documented breeding stock and keep careful records rather than relying on a retail colour label.

Appearance and Natural Variation

A Berlin Swordtail may have a warm red, scarlet or orange-red base with black speckles, patches or larger irregular areas. The distribution is individual. Some fish can be much more heavily marked than others, and young fish may not resemble a mature display specimen. Lighting, substrate, plant shade, stress, camera processing and screen settings can all change how saturated a fish looks. Colour should be judged as living variation, not matched to a digital swatch.

Adult males are associated with the elongated lower rays of the caudal fin that create the sword-like profile. Females are often larger-bodied and do not normally carry the same male sword. A young fish in a commercial size band may not yet show reliable mature differences, and finnage can be obscured in a bag or photograph. For that reason, the option selector refers to size, not sex.

The four current gallery images are representations created from reference material. They help communicate the red-and-black Berlin appearance, but their saturation, sword length, body proportions, plant scale and group composition are illustrative. The image with two fish is not a pair or quantity promise. No image is claimed to show the exact animal selected for dispatch, and a naturally different pattern is not a product defect.

Size Options and What One Quantity Means

Live size options describe an approximate commercial band available at the time of selection. They are not exact nose-to-tail measurements, age grades or sex guarantees. A fish close to a band boundary may change between supplier measurement and arrival because measuring a moving live animal is imprecise. The option price and availability shown beside the selector are the current source of truth; prices written into long descriptions quickly become stale and are deliberately excluded.

Is This Swordtail Right for Your Aquarium?

Body size alone can make a swordtail look like a simple community choice, but activity and social behaviour require more thought. The aquarium must offer at least 80 cm of uninterrupted horizontal length as well as at least 80 litres of real volume. Decorations, substrate and an air gap reduce usable water, so calculate the interior dimensions with the tank-volume tool. Then account for every adult fish, not only the specimens being added today, with the stocking calculator.

A prepared beginner can keep Berlin Swordtails successfully when the aquarium is fully cycled, the tap water is compatible, and there is enough room for adult behaviour. The species is less suitable for a tiny starter tank, very soft acidic water, an uncovered aquarium, or a crowded display where all surface and midwater space is already occupied. A fish described as hardy can still be harmed by ammonia, unstable temperature, harassment or chronic lack of swimming room.

Plan for the whole life of the fish. The smallest available option is not the final size, and a mixed-sex purchase may later produce fry even when no male is currently visible because female livebearers can store sperm. If your aquarium has no safe capacity for additional adults or fry, choose the group and companions with that possibility in mind before checkout.

Aquarium Size, Shape and Layout

Use 80 litres and 80 cm length as minimum thresholds, not an ideal ceiling. A long aquarium gives active fish more usable movement than a tall narrow tank of similar volume. Groups, mixed sexes and community companions increase the demand for footprint, visual breaks and filtration. A larger setup also makes it easier to divide attention from persistent males and to keep water chemistry stable between maintenance visits.

Keep an open lane through the middle and upper water while planting the back and sides. Dense stems, floating-root cover and branching decor can provide retreat without turning the aquarium into an obstacle course. Leave clear access around the filter intake, heater and testing points. Berlin Swordtails are capable jumpers, especially when startled, so use a secure lid and close gaps around cables and pipework.

Water Parameters and Stability

This page recommends 23-27 C, pH 7.0-8.0, 9-19 dGH and 3-10 dKH. The temperature and pH ranges are the conservative overlap between the supplier, OATA and FishBase. Hardness sources are broader: FishBase gives 9-19 dGH, OATA's combined Platy and Swordtail sheet gives 4-12 dGH, and supplier data extends much further. The narrower FishBase range is used as a practical species guide, with OATA's 3-10 dKH recorded separately.

Do not use the edges as daily targets or repeatedly add chemicals to move from one acceptable value to another. Test the aquarium and tap water, identify a stable point within a useful overlap, and select companions that share it. The water matcher can organise comparisons, but a test result and the needs of every inhabitant still decide suitability.

Ammonia and nitrite must remain at 0 mg/l. OATA advises keeping nitrate no more than 20 mg/l above the normal tap-water baseline. That wording matters in the UK because source-water nitrate varies. Record tap and aquarium results with the same reliable kit, then adjust stocking, feeding, plant growth and water-change frequency to control the difference rather than assuming one schedule works everywhere.

Cycle, Filtration and Oxygen

A new tank containing water is not automatically cycled. Beneficial microbial communities need time and a controlled ammonia source to establish in the filter. Before adding live fish, confirm that the system can process waste and returns 0 ammonia and 0 nitrite under its intended load. The guide to the fish-tank nitrogen cycle explains the process and why a fixed number of elapsed days is not proof.

Choose filtration for the real stocked volume and the waste produced by active omnivores. The filter should move and oxygenate water throughout the aquarium without forcing fish to swim constantly against a concentrated jet. Protect strong intakes where smaller fish or fry could be drawn in. Read the overview of aquarium filtration before replacing media or altering flow, because removing mature biological media can destabilise an otherwise established tank.

Good surface movement supports gas exchange, but bubbles alone do not remove dissolved waste. Warm water holds less oxygen than cool water, and oxygen demand can rise with crowding, bacterial activity or decaying food. Watch the whole aquarium, especially after maintenance and during hot weather. Persistent surface gasping, unusually rapid gill movement or fish clustering at the return needs immediate water and equipment checks.

Feeding an Omnivorous Swordtail

Xiphophorus hellerii is omnivorous. Use a complete, appropriately sized flake or granule as the staple, ideally with a meaningful algae or plant component, and rotate suitable frozen or live foods for variety. FishBase records worms, small crustaceans, insects and plant matter in the species' diet, while OATA specifically recommends a quality food with high algae content for platies and swordtails. A varied plan is more defensible than labelling the fish a pure herbivore or feeding rich animal foods alone.

Offer a measured amount that the fish can finish without food collecting behind decor or entering the filter. Watch each individual rather than feeding by habit. Faster fish can intercept floating food, while timid or newly arrived animals may need smaller particles distributed across more than one point. Adjust quantity to body condition, group size, food density, temperature and measured water quality. There is no universal spoonful or minute count that fits every aquarium.

Remove persistent leftovers and investigate repeated refusal to eat. One missed feed after transport is different from a continuing loss of appetite combined with clamped fins, laboured breathing, isolation or weight loss. Avoid using treats as a cure for poor staple nutrition, and do not overfeed fry food to adults. The filter has to process everything that enters the aquarium, whether or not a fish eats it.

Behaviour and Social Structure

Berlin Swordtails are active rather than tightly schooling. Individuals explore the middle and upper water, investigate food and interact regularly. A group can spread attention and display more natural social behaviour, but extra fish also require extra space. OATA recommends keeping at least three swordtails and using at least two females per male. That is a husbandry goal when sexes are known, not a retail promise from an unsexed option.

Male-to-male competition may include parallel swimming, posturing, chasing and attempts to control preferred areas. Persistent courtship can also exhaust a female if there is no refuge or if attention is concentrated on one fish. Larger footprint, planted sight breaks and a sensible group structure help, but no ratio guarantees harmony. Observe individuals and be prepared to separate a fish that is being injured or prevented from feeding.

Do not confuse constant frantic movement with a lively personality. Repeated dashing, hiding, glass surfing, clamped fins, surface gasping or refusal to leave one corner can indicate stress. Check water, temperature, oxygen, recent changes and social pressure before assuming the fish is simply energetic. A settled swordtail should use the aquarium confidently without being forced to flee another inhabitant all day.

Sexing and the Unsexed Sale Boundary

Mature males usually develop a gonopodium, a modified anal fin used in reproduction, and the familiar lower caudal extension. Mature females generally retain a fan-shaped anal fin, often develop a fuller body and can reach a larger total length. These features are useful in established adults, but young size bands, individual development, folded fins and transport posture can make sex uncertain.

One quantity on this page is therefore one unsexed fish. Selecting three does not create a guaranteed one-male, two-female trio. The pair-style gallery image is illustrative and does not change the unit. A visible sword in representative artwork also does not mean a male will be dispatched. This boundary protects both the customer and the fish from an expectation the live stock cannot reliably meet.

If a particular sex is essential for an existing group, do not infer it from option size or order quantity. Consider whether your aquarium can safely manage either sex and possible fry before ordering. A female may already have stored sperm from earlier contact with a male, so removing males does not guarantee that no future brood will appear.

Community Compatibility

Compatibility is a comparison of adult size, mouth size, water chemistry, temperature, activity, feeding speed, territory and available space. Berlin Swordtails often suit mineral-bearing peaceful communities, but the word community is not a blanket approval. Every companion still needs its own adequate group and adult footprint. Use the swordtail category to compare related forms without assuming they can all be added to one aquarium.

Livebearing and Fry Planning

Swordtails are livebearers: fertilisation occurs internally and females give birth to free-swimming young rather than laying a clutch of eggs for parental care. OATA notes that a female can produce roughly 20-80 fry, although age, size, condition and individual biology create wide variation. A retail fish is not sold as pregnant, fertile or proven, and no breeding result is guaranteed.

Adults may eat fry. Fine plants and floating roots can increase hiding opportunities, but they do not guarantee survival or solve a stocking problem. A breeder trap should not become prolonged cramped housing. If fry are expected, prepare a mature filtered rearing space, suitable tiny food, safe intake protection and a realistic plan for every surviving juvenile before breeding occurs.

Berlin pattern inheritance can be complex because cultivated swordtail forms have a long history of selection and crossing. Without documented parentage, do not advertise offspring as pure Berlin stock or assume that every juvenile will copy the adults. Keep records, avoid accidental mixing of named lines if provenance matters, and never release unwanted aquarium fish or water into the wild.

Health Observation and First Checks

A healthy settled swordtail should maintain balance, use the water column, respond to its surroundings and show an appropriate appetite. Fins are normally held rather than continuously clamped, breathing is not persistently laboured, and the body should not progressively thin. Temporary paleness or quiet behaviour after transport can occur, but duration and accompanying signs matter.

White spots, ragged fins, cotton-like growth, ulcers, flashing, persistent shimmying, swollen scales, unusual waste or rapid weight loss are observations, not diagnoses. Several diseases and environmental problems can look similar. Begin with accurate ammonia, nitrite, nitrate, pH and temperature checks, inspect equipment and review recent additions. Seek an aquatic veterinarian or experienced qualified professional where signs are severe, persistent or unclear.

Do not medicate the display aquarium on a guess. Treatments can affect filtration and may be dangerous to invertebrates or particular fish. Follow the product label and professional advice, calculate true water volume, and never combine medicines unless their instructions explicitly permit it. Correcting water quality is essential when a test is unsafe, but large abrupt chemistry changes can add further stress.

Quarantine and Biosecurity

A separate established quarantine system allows observation before a new fish joins the main aquarium. It should have mature filtration, heat, a secure lid, simple shelter and equipment that is not shared wet between systems. The appropriate observation period depends on risk, symptoms, source and professional guidance; a fixed number of days is not a guarantee that every pathogen has been excluded.

Use dedicated nets, siphons and towels where possible. Wash hands and avoid moving water, decor or filter media from quarantine into the display without a reasoned biosecurity plan. Record appetite, breathing, waste, swimming, skin and fin changes. Preventive medication without evidence can mask signs, expose fish unnecessarily and complicate later diagnosis.

Quarantine is not a substitute for a cycled main aquarium. Both systems must have safe water, and the final transfer still requires a temperature and water-chemistry plan. If the quarantine aquarium cannot house the fish comfortably at the selected size, prepare an appropriately larger system before the order arrives.

Preparing for Delivery

Complete the aquarium plan before checkout. Confirm 0 ammonia and 0 nitrite, record nitrate and source-water values, check temperature and pH, inspect the lid, and make sure the filter and heater have operated reliably. Keep suitable food available and leave room in the stocking plan for the adult fish. Review the current livestock delivery information so someone can receive the parcel promptly.

On arrival, inspect the unopened bag and follow the instructions supplied with the order. Do not pour transport water into the display aquarium. The correct method depends on the shipment and water difference, so use the acclimation timer alongside the full guide to acclimating new fish. Keep lighting subdued and avoid crowding the bag with curious pets or people.

If there is an arrival concern, document the unopened bag and fish promptly and follow the published returns and Live Arrival Guarantee terms. The guarantee is subject to those conditions; it is not an unlimited promise covering later husbandry, compatibility or ignored reporting requirements. Clear evidence helps the support team assess a genuine transit issue fairly.

Ordering, Current Availability and First-Order Offer

The option selector shows current live sizes, price and availability. Description copy deliberately does not hardcode a price because stock and size options can change. Select a size, then select the number of individual unsexed fish your aquarium can responsibly support. A multi-buy display may adjust pricing when several fish are selected, but it does not turn one quantity into a pair or guarantee a sex ratio.

Customers seeking a Berlin Swordtail for sale in the UK can use this page to compare current variants and care before deciding. WELCOME10 offers 10% off an eligible first order under the current promotion terms. Check the special offers page for eligibility and exclusions rather than assuming every item, customer or combination qualifies.

Tracked livestock delivery and the qualified Live Arrival Guarantee are useful purchase details, but they should support rather than crowd the search result. No listing can guarantee an image, discount line or other enhancement in Google because the search engine chooses the final result presentation.

Other Swordtails to Compare

Choose by identity and husbandry, not by adding every colour name to one page. The Green Swordtail offers a more natural-looking form, while the Black Swordtail is a darker cultivated option. The Kohaku Swordtail has a different red-and-white emphasis. Each is a separate product with its own availability and representative media.

The Albino Koi Swordtail and Berlin Lyra Swordtail should not be treated as synonyms for this standard Berlin form. Lyra describes different finnage, and albino koi describes a different appearance. Compare adult needs and current options on the destination page before mixing forms.

Multiple swordtail forms in one aquarium can produce visually varied offspring and make line records difficult. A colour-themed display and a breeding project are not the same goal. If you only want a peaceful display group, prioritise space, water overlap and sex pressure. If you intend to preserve a named form, source documented stock and separate breeding lines deliberately.

Long-Term Care Checklist

Evidence and Care References

Taxonomic identity was checked against Eschmeyer's Catalog of Fishes, which treats Xiphophorus hellerii as valid. Species-level size, distribution, diet and water information was cross-checked with the FishBase species summary. These sources describe the species and do not prove the breeder or collection origin of this retail stock.

UK-oriented aquarium guidance comes from OATA's Platy and Swordtail care sheet. Historical context for the cultivated name comes from Aquarium Glaser's Berlin Swordtail note. Where sources give different ranges, this listing explains the difference and uses a conservative practical overlap rather than silently choosing the broadest number.

Care guidance cannot account for every aquarium, local water supply or individual fish. Test your own water, consider every current inhabitant and seek specialist help when health signs or compatibility are uncertain. Scientific references improve factual grounding; they do not make a product page a veterinary diagnosis or a guarantee of outcome.

Frequently Asked Questions

What is the correct scientific name for the Berlin Swordtail?

The accepted species name is Xiphophorus hellerii. Berlin is a cultivated aquarium trade form, not a separate subspecies. The supplier spelling with one i is not used as the accepted taxonomic name.

Is Berlin Swordtail the same as Red Marble Swordtail?

Red Marble has been used as a loose visual or historic catalogue description for the red-and-black pattern. This listing uses Berlin Swordtail as the primary identity because it matches the supplier trade name and avoids unrelated marble-stone meanings.

How large does a Berlin Swordtail grow?

OATA gives 8-12 cm for swordtails. FishBase reports maximum total lengths of about 14 cm for males or unsexed fish and 16 cm for females. Different measurement conventions and the male sword extension explain why figures vary.

What is the minimum tank size?

Provide at least 80 litres and at least 80 cm of aquarium length. Use more volume and footprint for a group, mixed sexes or community companions. A tall but short aquarium does not meet the swimming-length need.

What temperature should Berlin Swordtails have?

Keep a stable temperature within 23-27 C. This is the complete overlap between the supplier, OATA and FishBase ranges. Match all companions to the same useful point and avoid abrupt changes.

What pH and hardness do they need?

Use pH 7.0-8.0, 9-19 dGH and 3-10 dKH as practical guidance. Test the source and aquarium water, and favour stable compatible chemistry over repeatedly dosing towards an extreme value.

Are Berlin Swordtails easy to care for?

They are robust when their needs are met, but this page rates care as moderate. Adult swimming room, mineral-bearing water, mature filtration, social pressure, feeding and possible fry all require planning.

How many should I keep?

OATA recommends at least three swordtails. A larger group needs more aquarium capacity. When sexes are reliably known, at least two females per male may spread courtship, but individual behaviour still needs observation.

Can I choose male or female?

No. Fish on this page are sold unsexed. Size, quantity and gallery finnage do not guarantee sex. Order only if your aquarium can safely accommodate either sex and the possibility of later fry.

Does one quantity mean a pair?

No. One selected quantity means one unsexed fish in the chosen available size band. The image showing two fish is representative social artwork and is not a pair, group or quantity promise.

What should I feed a Berlin Swordtail?

Use quality complete flake or granules with a meaningful algae or plant component, plus measured suitable frozen or live foods for variety. Watch each fish eat and remove persistent leftovers.

Can Berlin Swordtails live with guppies, mollies or platies?

They can in some larger mineral-bearing communities, but it is not automatic. Compare adult load, temperature, pH, hardness, activity, feeding, sex pressure and hybridisation concerns before mixing livebearers.

Can they live with a betta?

Do not treat a betta as a default companion. Individual temperament, fin nipping, activity, territory, water overlap and feeding competition can create conflict, and a separate setup may be needed.

Are they safe with shrimp?

No blanket safety guarantee is possible. Adult shrimp may coexist in some planted aquariums, but small shrimp and shrimplets can be investigated or eaten. Choose a dedicated shrimp setup when survival is the priority.

Will the fish match the gallery exactly?

No. The four images are representations, not photographs of the exact fish dispatched. Natural pattern, colour, sex, sword length, fin shape, body proportions and size appearance vary.

Will Berlin Swordtails breed in a community aquarium?

They may. Swordtails give birth to live fry, and females can store sperm. Adults may eat young, while surviving fry add to the aquarium's load. Plan mature rearing space and future homes before encouraging breeding.

Why might a newly arrived fish look pale?

Transport, bright light and a new environment can temporarily reduce visible colour. Keep conditions calm and test water, but investigate persistent paleness when it accompanies rapid breathing, clamped fins, poor balance or refusal to eat.

What should be ready before I order?

Prepare at least 80 litres and 80 cm length, mature filtration, a secure lid, suitable tested water, a stable heater, appropriate food, adult stocking capacity and time to receive and acclimate the delivery promptly.