Black and White Platy (Xiphophorus maculatus)

Bring bold contrast with the Black and White Platy

The Black and White Platy is an aquarium-bred colour form of the common platy, Xiphophorus maculatus, and every fish wears its own pattern. Our photographs show a pearly white body with a pink flush on the gill cover and a pale blue ring around the eye. Black blotches are scattered over the top of the head and shoulder, then gather into a solid block of black across the rear half of the body, from beneath the dorsal fin down to the tail base. The tail and the other fins are clear and glassy, with a little black where they join the body.

It is a small, peaceful, easy-going fish that suits a planted community tank in hard water, and its two-tone colouring stands out from across the room. Seriously Fish rates the common platy as suitable for beginners provided the water is moderately hard or harder, which much UK tap water already is.

Read the label correctly

Tell it apart from similar platies

Platy breeders have produced many black-and-white combinations, and Seriously Fish lists wagtail, Mickey Mouse, moon, tuxedo and comet among the established varieties. Our Salt and Pepper Platy is speckled evenly all over. The White Mickey Mouse Platy is white with a small three-spot mark at the tail base, the pattern you can see clearly on the classic Mickey Mouse Platy, and our Mickey Mouse platy guide explains that pattern in detail. The Blue Wagtail Platy keeps its black for the fins. The Black and White is the bolder fish: a white front and a solid dark rear.

Know what to expect on arrival

Your order brings one live Black and White Platy of medium size per purchase, a young fish with some growing left. Sex is not chosen or guaranteed. Males are smaller with a pointed anal fin, the gonopodium; females are larger, deeper-bodied and have a fan-shaped anal fin. Because the black patching is irregular, your fish will carry its own arrangement of marks, and young platies of patterned forms can gain or shift black as they grow. White fish also look slightly translucent and pale for a day or two after travel.

Decide on numbers

• Three fish: OATA's minimum group, one male to two females.
• Six fish: a fuller group where each fish's pattern can be told apart.
• A mixed black-and-white group: add Salt and Pepper or Mickey Mouse platies only if you are happy for the patterns to mix in the young.

Check our delivery and Live Arrival Guarantee page before ordering, and make sure the aquarium is cycled and stable.

Choose the right aquarium for a black and white platy

Adult platies are small. OATA gives 6–8 cm; FishBase records 4.0 cm total length for males and 6.0 cm for females; Seriously Fish gives 50 mm standard length, measured from snout to tail base. The figures differ, but the fish stays small and the females end up bigger than the males.

OATA's minimum for a small platy group is 45 litres. Seriously Fish suggests a 60 × 30 cm base, about 54 litres, and FishBase gives a 60 cm minimum tank length. Platies are frequently recommended as a first fish, and our list of the best tropical fish for beginners shows which others fit the same hard-water tank.

Check the space in three steps

1. Base: 60 cm long, 30 cm front to back.
2. Volume: 45–54 litres or more of actual water.
3. Future: run the numbers through our stocking calculator with room for a brood or two.

Set the scene for a two-tone fish

FishBase describes the platy's wild home as warm springs, canals and ditches with slow water, silt bottoms and weedy banks, as well as creeks and swamps. Plants, gentle flow and calm water suit it. A black-and-white fish shows best against mid-green plants and a medium-toned substrate, where both the white front and the black rear stay visible.

Zone the aquarium

Leave some algae on rocks and wood for the fish to graze. A lid prevents jumping and reduces evaporation; OATA calls it optional but advisable.

Hold the water hard and alkaline

Seriously Fish states that platies need moderately hard or harder water, do best with the pH above neutral and will not thrive in soft, acidic water. The sources agree on pH, broadly agree on temperature and differ on hardness, so the table shows each one.

Compare the sources

Dechlorinated tap water from a hard-water area usually suits platies without further treatment. If you live in a soft-water area, check your readings before buying: enter them in our water matcher and read the water chemistry guide for what GH, KH and pH mean in practice.

Look after the filter and the water

Seriously Fish suggests filtration of four to five tank volumes an hour, about 215–270 litres per hour for a 54-litre tank, and a heater of about 50 W in a room near 20°C. A steady routine keeps waste from the fish and their young under control.

Weekly maintenance

1. Test ammonia, nitrite, nitrate, pH and hardness, as OATA recommends.
2. Change 25% of the water using dechlorinated water at tank temperature.
3. Vacuum the substrate and remove dead leaves.
4. Rinse filter media gently in old tank water, never tap water.
5. Keep a count of fish and fry.

Feed it once a day

FishBase lists worms, crustaceans, insects and plant matter as the platy's natural foods, and Seriously Fish says it accepts frozen, live and dried foods. OATA recommends a quality flake or granule rich in algae, fed once daily in an amount eaten within a few minutes, with occasional live or frozen food. Overfeeding fouls the water faster than anything else in a small tank.

Size each portion

• Staple: algae-rich flake, crumbled small.
• Extras: Daphnia, brine shrimp or bloodworm two or three times a week, replacing some of the flake.
• Amount: what the group finishes in a few minutes; remove leftovers.
• Fry: powdered food or brine shrimp nauplii two or three times a day (Seriously Fish).

Acclimatise it carefully

Have ammonia and nitrite at zero, a mature filter and water at 20–25°C and pH 7.0–8.0 before the fish arrives. OATA's floating-bag method: switch off the lights, float the sealed bag for about 10 minutes, add small amounts of tank water over up to 20 minutes, then net the fish into the tank and dispose of the bag water. See our guide to acclimatising new fish for more detail.

Follow the first week

Keep it with gentle hard-water fish

Seriously Fish calls the common platy very peaceful and suitable for most community tanks. Males tolerate each other but court females relentlessly, which is why OATA recommends at least three fish, two females per male. Pick tank mates that share the hard water and will not race the platies to every meal.

Choose companions

Use our tank mates tool to check a mix. Browse more platies and livebearer fish, the platy category page and our southern platy varieties. The platy care guide goes further into keeping and breeding.

Raise the young or keep numbers steady

Platies give birth to live young after internal fertilisation. FishBase gives 24–30 days' gestation, 20–80 young per brood and sexual maturity at 3–4 months; Seriously Fish gives about four to six weeks and broods of up to 80. Adults eat newborn fry, so plant cover decides how many survive in a community tank.

Pick a plan

1. Hands-off: dense plants and floating cover let a few fry grow up naturally.
2. More fry: Seriously Fish suggests moving a heavily pregnant female to a separate tank for the birth and returning her afterwards; OATA describes a breeding net, which Seriously Fish does not recommend.
3. Rearing: two or three tiny meals a day.
4. No fry: keep a single-sex group.

Black-and-white young from a black-and-white pair will still vary; every fish in a brood can have a different arrangement of black.

Keep an eye on health

Seriously Fish warns that many commercially bred platies are prone to disease and early death because of inbreeding and over-production. OATA's warning signs are clamped fins, flicking or shaking, hanging at the surface or sitting on the bottom, colour darker or paler than normal, white spots or fluffy growths, lost fins or scales, changed breathing and a reduced appetite.

Match each sign with a first step

White spots can be harder to see on a pale fish, so look closely during the first weeks. The black patches themselves are pigment-cell markings of the kind scientists have studied for decades: Meierjohann and Schartl (2006) review how certain platy-swordtail crosses develop melanoma, and FishBase notes that the species is used in genetic research. FishBase also records ecological harm in at least one country where platies were introduced, so never release unwanted fish; return them to a shop or another keeper.

Answer Black and White Platy buying questions

What is a Black and White Platy?

It is an aquarium-bred colour form of the common platy, Xiphophorus maculatus. Our photographs show a pearly white fish with a pink-flushed gill cover and a pale blue eye ring, scattered black blotches on the head and shoulder, and heavy black covering the rear half of the body from under the dorsal fin to the tail base. The tail and fins are clear with a little black at their base.

Is it the same as a Salt and Pepper Platy?

No. Both are black-and-white forms of the same species, but the Salt and Pepper is speckled all over, while the Black and White on our photographs has a mostly white front half and a solid block of black over the rear half. Care is identical, and the two will interbreed.

Will every fish have the same pattern?

No. In platies with this kind of black patching, no two fish carry exactly the same marks, and the black can spread or shift as a young fish grows. Expect a white fish with black concentrated towards the tail, not a copy of the photograph.

How big does it grow?

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 50 mm standard length, measured without the tail.

What size aquarium is needed?

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

What water does it need?

Hard, alkaline water at pH 7.0–8.0 and 20–25°C, where OATA, FishBase and Seriously Fish overlap, with about 10–12 dGH to satisfy all three hardness ranges. Seriously Fish says platies will not thrive in soft, acidic water.

Is it a good fish for beginners?

Yes, provided the water is moderately hard or harder. Seriously Fish rates the common platy as suitable for beginners on that condition, and it is peaceful, small and easy to feed.

Will it breed?

Almost certainly, if both sexes are present. FishBase gives a 24–30 day gestation, 20–80 young per brood and maturity at 3–4 months.

How many fish come with one purchase?

One live fish of medium size. Sex is not chosen or guaranteed, and the black and white pattern is unique to each fish.

Check the sources behind this guide

• Seriously Fish: Xiphophorus maculatus — maximum size, aquarium base, water values, filter and heater sizing, diet, behaviour, sexing, 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, habitat, natural diet, maturity, gestation, brood size, minimum aquarium length, IUCN status and introductions.
• OATA: How to look after swordtails & platies — UK trade-body guidance for platies and swordtails: adult sizes, tank volumes, water values, group size and sex ratio, feeding, acclimatisation, maintenance, breeding and health signs.
• Meierjohann & Schartl 2006, Trends in Genetics: From Mendelian to molecular genetics: the Xiphophorus melanoma model — peer-reviewed review of why crosses between platies and swordtails are a long-standing research model for pigment-cell tumours (melanoma).
• Tropical Fish Co delivery policy — current dispatch days and Live Arrival Guarantee terms.