Sailfin Molly (Poecilia velifera) - Pack of 10

This listing is for a pack of 10 Sailfin Mollies (Poecilia velifera). The recorded supply size is over 5 cm per fish. They are sold as an unsexed group, so the colour, pattern, sex ratio, pregnancy status and height of the dorsal fin will vary and cannot be selected. Plan for the full adult group before ordering: this is a large, active livebearer, not a small molly for a soft-water nano aquarium.

The Yucatan or Giant Sailfin Molly is valued for its broad body, steady grazing behaviour and the tall, sail-like dorsal fin developed most strongly by mature males. It is generally peaceful with suitable companions, but it needs hard, alkaline water, excellent filtration and much more swimming room than its delivery size suggests.

Order and Care at a Glance

What Makes Poecilia velifera Different?

Poecilia velifera is the large sailfin species associated with Mexico's Yucatan Peninsula. It is related to, but not identical with, the smaller Poecilia latipinna that also appears under the name Sailfin Molly in the aquarium trade. FishBase and the Smithsonian's Shorefishes database record P. velifera at around 15 cm maximum length, which is why adult space and filtration must be planned from the start.

Mature males can raise a high, patterned dorsal fin during courtship and display. Females and younger fish usually have a lower fin and fuller body. Commercial fish may show variable colour and may have domestic ancestry, so this listing guarantees the supplied trade identity, group quantity and recorded size band, not an exact wild phenotype or a particular colour strain.

Aquarium Size and Setup for a Pack of 10

For this ten-fish pack, use a mature aquarium of at least 300 litres with a frontage of 120 cm or more. That recommendation allows for adult body size, constant activity, grazing, waste production and social pressure within the group. A larger aquarium is preferable when several males are present, when fry may be retained or when other fish already occupy the same swimming space.

Build the layout around open water rather than dense decoration. Use planted or structured margins for retreat, then preserve a broad central and upper swimming area. Robust plants, wood and rock can create visual breaks, but every item should leave enough turning room for a deep-bodied adult. A secure lid is sensible, and strong biological filtration with good surface movement helps support the oxygen demand and waste load of a large livebearer group.

Cycle the aquarium fully before arrival. Ammonia and nitrite must remain at zero, while nitrate should be controlled through stocking discipline, plant growth and regular partial water changes. Match replacement water for temperature and mineral content so routine maintenance does not create abrupt swings in pH or hardness.

Hard, Alkaline Water Is Essential

Aim for 25-28 C, pH 7.5-8.0 and roughly 13-19 dGH as a stable core range. The recorded source range is broader, but the narrower target is easier for shoppers to use and aligns with published species data. Soft, acidic water can leave mollies struggling to regulate minerals even when the temperature appears correct. If your tap water is naturally soft, test it before ordering and use a consistent remineralisation method rather than making irregular corrections after the fish arrive.

This species occurs in fresh and brackish habitats, but that does not mean every aquarium needs salt. Controlled research on P. velifera found better growth performance in freshwater than at higher salinities. Routine salt is therefore unnecessary when hard, alkaline freshwater is stable, well oxygenated and clean. Never add salt casually to a community aquarium without checking the tolerance of every fish, plant and invertebrate.

Behaviour, Sex Ratio and Fry

Sailfin Mollies are social, visible fish that spend much of the day swimming, grazing and investigating food. Mature males may extend the dorsal fin, spar with one another and pursue females. The ten fish in this pack are unsexed, so a specific male-to-female ratio cannot be guaranteed. Provide generous space and several broken sight lines, then watch whether any individual is being followed continuously or excluded from feeding.

Like other mollies, they are livebearers. A mixed-sex group can produce fry, and females may already be carrying stored sperm or developing young when supplied. Dense plant cover can increase fry survival, but the main aquarium must still be sized for the adults. Do not use a small breeding box as long-term accommodation for a female.

Tank Mate Guide

Water compatibility comes before appearance. A peaceful fish that needs soft acidic water is not a good companion simply because it is non-aggressive. The pack already contains ten active adults-in-training, so calculate the final biological load before adding more fish.

Feeding for Body and Fin Condition

Use a quality complete flake or granule as the base diet, choosing one with a meaningful algae or vegetable component. Rotate spirulina foods, suitable algae wafers or plant-rich soft foods with small portions of daphnia, brine shrimp, mosquito larvae or similar frozen foods. Published field work has found substantial green algae and plant material in the diet of wild P. velifera, alongside some animal prey, so an all-meat diet is not appropriate.

Offer small portions that the group can finish promptly, distributing food across the surface so less assertive fish get access. Mollies also graze on biofilm and algae between meals. That useful grazing does not make them a substitute for aquarium maintenance, and overfeeding a ten-fish group can quickly undermine water quality.

Arrival and the First Week

1. Have the aquarium heated, cycled and matched to the target hard-water range before dispatch.
2. On arrival, keep the room calm and the aquarium lights low.
3. Follow the livestock acclimation instructions and avoid prolonged opening or handling of the transport bags.
4. Release the group into open water with nearby cover, then allow them to settle before feeding lightly.
5. During the first week, check respiration, posture, fin position, appetite and whether any fish is being chased away from food.

Shimmying, clamped fins or persistent surface distress are reasons to test temperature, pH, hardness, ammonia, nitrite and oxygenation immediately. Salt should not be used as a substitute for identifying the underlying water or stocking problem. Our acclimation timer can help you organise the arrival process, while the live-fish delivery page explains packing and guarantee steps.

Is This Pack Right for Your Aquarium?

• Choose it if: you have a mature 300-litre-or-larger hard-water aquarium, want a substantial social group and can support a possible mixed-sex livebearer population.
• Reconsider if: your aquarium is soft and acidic, shorter than 120 cm, already heavily stocked or intended for timid nano fish.
• Expect natural variation: the fish are unsexed and may differ in colour, pattern, body shape and fin development.
• Plan beyond delivery size: fish recorded at over 5 cm can mature towards approximately 15 cm.

Frequently Asked Questions

How many fish are included?

One product quantity includes a pack of 10 Sailfin Mollies. The GBP 91.99 product price is for the complete ten-fish pack, not for one fish.

Can I choose males, females or a colour?

No. The pack is supplied unsexed, and colour, pattern, pregnancy status and dorsal-fin development are not selectable or guaranteed.

What tank size does this pack need?

Plan at least 300 litres and 120 cm of swimming length for the ten-fish group, with more space where other fish, several males or retained fry increase the load.

Do Sailfin Mollies need aquarium salt?

No routine salt is required in stable, hard, alkaline freshwater. Although the species can live in brackish environments, research has recorded better growth performance in freshwater than at elevated salinity. Only use salt for a defined purpose after checking every tank inhabitant.

Are these true Poecilia velifera?

The supply record identifies them as Poecilia velifera. Exact wild provenance, genetic purity and a particular colour strain are not guaranteed for commercial aquarium stock.

Will the fish look exactly like the gallery image?

No. The gallery uses a representative aquarium image to show the species type. It is not a photograph of the exact ten fish dispatched and does not guarantee colour, sex, scale or fin development.

Delivery, Guarantee and Related Fish

Eligible livestock orders are packed for UK live-fish transport and covered by our Live Arrival Guarantee. New customers can use the first-order 10% discount shown in the store journey, subject to its current terms. Browse the wider Mollies collection, compare other livebearers, or return to all freshwater fish before finalising stocking.

Evidence Behind This Care Guide

Species identity, adult size, native range and water guidance were checked against recognised fish databases and peer-reviewed research. Aquarium-size advice is deliberately conservative for this specific ten-fish pack and should be increased when the existing stock or layout reduces usable swimming space.

• FishBase: Poecilia velifera
• Smithsonian Tropical Research Institute: Yucatan Molly
• Journal of Applied Aquaculture: salinity tolerance and development
• Water: trophic ecology of Poecilia velifera