White Moon Platy (Xiphophorus maculatus)

Choose the White Moon Platy, a pearly platy with dark fins

The White Moon Platy is an aquarium-bred colour form of the common platy, Xiphophorus maculatus, one of the easiest and most popular livebearers you can keep. Our photographs show a pearly white body with a soft blue and pink iridescence, a pink-flushed gill cover, a few dark freckles on the shoulder and smoky black dorsal and tail fins. The dark colour gathers at the base of the tail, where platy breeders look for the "moon", a dark crescent-shaped mark.

Under the colour it is an ordinary platy: peaceful, small, hardy and happy in the moderately hard to hard tap water found across much of the UK. The pale body stands out well against green plants and a darker substrate, which makes it a good contrast fish in a planted community aquarium.

Check the names on the label

Tell it apart from our other white and patterned platies

Platies have been bred into many colours and patterns; FishBase notes that several colour varieties are popular aquarium fish and that the species is used in genetic research. The marks at the base of the tail are part of that variety. Our White Mickey Mouse Platy is also white, but its tail-base mark has two small dots beside it, like a cartoon mouse head, and its fins are clear; see the classic Mickey Mouse Platy for the full pattern. The Blue Wagtail Platy shows the wagtail pattern of black fins on a coloured body, and the Salt and Pepper Platy is speckled all over.

We want to be clear about our own photographs. On them the dark colour runs from the tail base into a smoky black tail and dorsal fin, so the moon is not sharply outlined. In this form the size, sharpness and darkness of the moon, and the darkness of the fins, vary from fish to fish.

Know exactly what you receive

One purchase supplies one live White Moon Platy of medium size, a young fish that is still growing. Sex is not chosen or guaranteed. Males are smaller and have a pointed, rod-like anal fin, the gonopodium; females are larger and rounder with a fan-shaped anal fin. Colour is often paler for a few days after the journey.

Decide how many to order

• Three fish: OATA's minimum group, ideally one male and two females.
• Six fish: a fuller display with two females to each male.
• A mixed platy group: combine with other platy colours only if you are happy for them to interbreed.

Read our delivery and Live Arrival Guarantee information before ordering, and have the aquarium filtered and matured before the fish arrive.

Plan the aquarium around the adult size

OATA gives adult platies as 6–8 cm. FishBase records 4.0 cm total length for males and 6.0 cm for females, and Seriously Fish gives a maximum of 50 mm standard length, measured without the tail. Whichever figure you use, this is a small fish that needs swimming space more than depth.

OATA asks for at least 45 litres for a small group of platies, Seriously Fish recommends a base of 60 × 30 cm, about 54 litres, and FishBase gives a minimum aquarium length of 60 cm. Larger tanks keep temperature and water quality more stable, as OATA notes, and absorb the extra fish that a breeding group produces. New to tropical fishkeeping? Our first tropical aquarium guide walks you through setting up from scratch.

Run a three-step space check

1. Measure the base: at least 60 cm long and 30 cm front to back.
2. Count adults: plan for fish of up to 6–8 cm, not the youngsters you receive.
3. Allow for fry: FishBase says platies mature at 3–4 months, so check your numbers in our stocking calculator as the group grows.

Plant densely with a dark floor

FishBase describes wild platies in warm springs, canals and ditches with slow-moving water, silt bottoms and weedy banks, as well as creeks and swamps, and Seriously Fish recommends dense planting for breeding groups. A white fish also shows best against dark sand or gravel and green plants.

Divide the tank by function

Platies graze on the soft algae that grow on plants and décor, so a little green growth on rocks is welcome. A lid stops an excited fish jumping and reduces evaporation; OATA calls it optional but advisable.

Set hard, alkaline water

Seriously Fish is direct: platies will not thrive in soft, acidic water and should be kept in moderately hard or harder water. The three sources agree on pH and broadly on temperature, and differ on hardness.

Read the sources side by side

Much UK tap water is moderately hard to hard and suits platies after a dechlorinator. If your supply is soft, talk to us before you buy. Compare your test results in our water matcher and read the water chemistry guide to see what each reading means.

Filter and maintain a small livebearer tank

Seriously Fish suggests a filter turning the water over four to five times an hour, about 215–270 litres per hour for a 54-litre tank, and a heater of roughly 50 W in a room near 20°C. Platies breed readily, so keep maintenance regular even when the tank looks clean.

Follow a weekly routine

1. Test ammonia, nitrite, nitrate and pH at least once a week, as OATA advises.
2. Change 25% of the water at least weekly with dechlorinated water at the same temperature.
3. Siphon waste from the substrate and remove dead plant leaves.
4. Rinse filter sponges in removed tank water, never under the tap.
5. Count the fish, including fry, so overcrowding never creeps up.

Feed algae-rich food once a day

Seriously Fish calls the platy unfussy: it accepts frozen, live and dried foods. FishBase lists worms, crustaceans, insects and plant matter in its natural diet. OATA recommends a quality flake or granule with a high algae content as the staple, fed once a day in an amount the fish finish within a few minutes, with occasional live or frozen food.

Build one measured meal

• Staple: algae-rich or vegetable flake, crushed for small mouths.
• Variety: Daphnia, brine shrimp or bloodworm a few times a week, replacing part of the staple.
• Portion: what the group clears in a few minutes; remove anything left over.
• Fry: Seriously Fish says fry accept brine shrimp nauplii or powdered flake from birth and should be fed two to three times a day.

Introduce the fish to a mature aquarium

Before arrival, confirm that the filter is mature, ammonia and nitrite read zero and the water sits at 20–25°C and pH 7.0–8.0. Follow OATA's floating-bag method: float the sealed bag for 10 minutes, add small amounts of tank water over up to 20 minutes, then release the fish without pouring in the bag water. Our guide on how to acclimatise new fish explains each step.

Use a first-week checkpoint plan

Keep a balanced group with peaceful tank mates

Seriously Fish describes the platy as very peaceful and suitable for most community tanks, notes that males tolerate one another, and warns that males can be relentless in their attention to females. OATA recommends at least three fish, with two females to each male.

Screen each companion

Check any planned mix with our tank mates tool. Browse all platy fish and livebearers, the platy category and our Xiphophorus maculatus platies. Our platy care guide and Mickey Mouse platy guide go further, and platies feature in our list of the best beginner tropical fish.

Breed platies or keep the numbers steady

Platies are livebearers: the male fertilises the female internally and she gives birth to free-swimming young. FishBase gives a gestation of 24–30 days, 20–80 young per brood and maturity at 3–4 months. Seriously Fish gives about 4–6 weeks and says broods of up to 80 fry are not uncommon.

Raise a brood

1. Plant densely: Seriously Fish recommends several females per male and plenty of plants.
2. Protect the fry: OATA suggests a breeding net for a heavily pregnant female, as adults eat fry.
3. Feed little and often: two to three small meals a day for the young.
4. Plan homes: decide where surplus youngsters will go, and never release them.

Seriously Fish notes that some platy varieties were produced by crossing with swordtails or variatus platies. To keep the white body and moon pattern, breed only White Moons together; mixed colours give mixed young.

Watch for problems early

Seriously Fish warns that many commercially bred platies are prone to disease and early death because of inbreeding and over-production, so good water and a calm first few weeks matter. OATA's warning signs are clamped fins, flicking against objects, shimmying, hanging at the surface or sitting on the bottom, colour change, white spots or fluffy growths, lost fins or scales, a changed breathing rate and reduced appetite.

Pair each sign with an action

FishBase notes that at least one country reports adverse ecological effects after platies were introduced. Return unwanted fish to a shop or another keeper and never release them into a pond or river.

Answer White Moon Platy buying questions

What is a White Moon Platy?

It is an aquarium-bred colour form of the common platy, Xiphophorus maculatus, a small livebearer from Mexico, Guatemala and Belize. "White" describes the pearly body; "moon" is the platy name for a dark crescent-shaped mark at the base of the tail. Our photographs show a white, iridescent body, a pink gill cover and smoky black dorsal and tail fins, with the dark colour gathering at the tail base.

Is it the same as a White Mickey Mouse Platy?

No. Both are white forms of the same species, but the Mickey Mouse pattern adds two small round dots to the tail-base mark, so it looks like a cartoon mouse head, and our White Mickey Mouse Platy has clear fins. The White Moon on our photographs has no dots and much darker fins.

How big does it grow?

OATA gives adult platies as 6–8 cm. FishBase records 4.0 cm for males and 6.0 cm for females, and Seriously Fish gives a maximum of 50 mm standard length, measured without the tail.

What size aquarium does it need?

At least 45 litres for a small group, according to OATA. Seriously Fish recommends a base of 60 × 30 cm, about 54 litres, and FishBase gives a minimum aquarium length of 60 cm.

What water does it need?

Hard, alkaline water at 20–25°C and pH 7.0–8.0, where OATA, FishBase and Seriously Fish all overlap. For hardness, 10–12 dGH satisfies all three sources, and harder water up to about 19 dGH fits both species profiles. Seriously Fish warns that platies will not thrive in soft, acidic water.

How many should I keep?

At least three, with two females to every male, as OATA advises. Seriously Fish says males tolerate one another but can be relentless towards females.

What does it eat?

Platies are unfussy omnivores. Feed an algae-rich flake or granule once a day, only as much as is eaten in a few minutes, with Daphnia, brine shrimp or bloodworm now and then.

Will it breed in my aquarium?

Yes, if males and females are kept together. FishBase gives a 24–30 day gestation and 20–80 young, and young platies mature in 3–4 months, so numbers can grow quickly.

How many fish come with one purchase?

One live fish of medium size. Sex is not chosen or guaranteed, and the size and sharpness of the moon mark vary from fish to fish.

Consult the care references

• Seriously Fish: Xiphophorus maculatus — size, aquarium base, water values, behaviour, gestation, brood size, named varieties and the warning about inbred commercial stock.
• FishBase: Xiphophorus maculatus — maximum recorded lengths of males and females, environment values, distribution, maturity, gestation and brood size.
• OATA: How to look after swordtails & platies — UK trade-body guidance for platies and swordtails: adult sizes, tank volumes, water values, sex ratio, feeding, breeding, acclimatisation and health signs.
• Tropical Fish Co delivery policy — current dispatch days and Live Arrival Guarantee terms.