How many guppies should I keep together?

Keep at least three to six. If you mix sexes, many keepers use about one male to two or three females so no single female is chased constantly. An all-male tank avoids breeding entirely.

Do guppies need a heater?

In most homes, yes. FishBase gives a range of 64–82°F, but guppies are healthiest and most colorful in stable warm water in the mid-70s °F. A heater prevents nighttime drops in cool rooms.

How often do guppies have babies?

FishBase reports that females store sperm and may give birth about every four weeks, with gestation of four to six weeks and broods of roughly 20 to 40 live young.

Do guppies eat their babies?

Yes. FishBase notes guppies provide no parental care and may eat their young. Dense plants such as java moss or a separate fry tank greatly improve fry survival.

How can I tell male and female guppies apart?

Males are smaller and more colorful with long tails, and their anal fin is a pointed gonopodium. Females are larger, often plainer, with a fan-shaped anal fin and a dark gravid spot when pregnant.

Can guppies live with bettas?

It is risky. Male bettas may attack long-finned, colorful guppies, and guppies may nip betta fins. If you try it, use a larger planted tank and be ready to separate them.

Guppy care: tank setup, water, feeding and breeding

Guppies (Poecilia reticulata) are among the best first fish: small, colorful, active and tolerant of beginner mistakes. They are also famous breeders — a single pair can fill a tank in a few months. This guide covers setup, water, feeding, breeding and health, using the FishBase species profile, the Merck Veterinary Manual on water quality and UF/IFAS Extension advice for aquarium owners. See all our fishkeeping guides in the aquarium library.

Where do guppies come from?

FishBase lists the guppy’s native range in northern South America and nearby islands — Venezuela, Barbados, Trinidad, northern Brazil and the Guianas — and notes it has been introduced widely around the world, with feral populations in several regions. That is one reason UF/IFAS Extension urges owners never to release aquarium fish: hardy species like guppies can establish themselves in the wild.

How big do guppies get?

Colorful male guppy and larger grey female — Illustration: male guppy (colorful) and female (larger, grey)

According to FishBase, males reach about 2 inches (5 cm standard length) at most and females about 2.4 inches (6 cm); a typical male is closer to 1.1 inches (2.8 cm). Males are about half the size of females. FishBase also reports males mature at about 2 months and females at about 3 months.

What tank do guppies need?

Item	Recommendation
Tank size	10 gallons minimum for a small group; 20 gallons for a mixed-sex colony
Filter	Gentle flow; a sponge filter is ideal because it won’t suck in fry
Heater	Adjustable, set to about 74–80°F
Lid	Yes — guppies can jump
Plants	Dense live plants such as java moss, hornwort and floating plants
Light	8–10 hours on a timer

Live plants are especially useful with guppies: they shelter fry and absorb waste. Our planted aquarium guide lists easy species.

What water parameters do guppies need?

Parameter	Target	Source
Temperature	64–82°F range; 74–80°F typical	FishBase range; keeper practice
pH	7.0–8.0	FishBase
Hardness	9–19 dH (moderately hard)	FishBase
Ammonia	0	Merck: normal is 0 mg/L
Nitrite	0	Merck: toxic above 0.1 mg/L
Nitrate	Under 20 mg/L	Merck: normal freshwater value

Guppies prefer slightly alkaline, moderately hard water, which matches many U.S. tap supplies. Very soft, acidic water is a common cause of trouble. Always treat tap water with a dechlorinator: the Merck Veterinary Manual reports harm to fish from chlorine at concentrations as low as 0.02 mg/L.

Before adding guppies, the tank must be cycled. Our aquarium cycling guide walks through the process step by step.

What do guppies eat?

Guppies are omnivores and eager eaters — which makes overfeeding easy.

Staple: quality tropical flakes or micro-pellets.
Variety: frozen or live baby brine shrimp, daphnia and bloodworms (chopped) a few times a week.
Vegetables: flakes with spirulina or algae.
Portion: what they finish in about two minutes, once or twice a day.

UF/IFAS Extension advises feeding in moderation to prevent obesity and excess ammonia.

How many males and females should I keep?

Males court females constantly. In mixed groups, keepers usually aim for one male to two or three females so the attention is spread out. Options:

Setup	Pros	Cons
All males	No babies, most color	Some chasing between males
All females	No babies (after any stored sperm is used up)	Less color
Mixed sexes	Natural behavior, fry	Population grows fast

Note that females can store sperm: FishBase says they may keep producing young roughly every four weeks, so a female bought from a mixed tank may give birth even if you keep no males.

How do guppies breed?

Guppies are livebearers. FishBase describes the details:

The male’s anal fin is modified into a gonopodium for internal fertilization.
Gestation lasts four to six weeks.
A brood is roughly 20 to 40 live young.
Pregnant females show a dark triangular “gravid spot” between the anal and pelvic fins.
Parents give no parental care and may eat their young.

How do I raise guppy fry?

Provide cover. Thick java moss or floating plants let many fry escape adults.
Or separate. Move a heavily pregnant female to a breeding box or separate tank shortly before birth, then return her afterward. Breeding boxes stress some females, so a separate planted tank is gentler.
Feed fry often. Crushed flakes, powdered fry food or baby brine shrimp, small amounts several times a day.
Keep water clean. Fry are sensitive; small, frequent water changes work best.
Plan ahead. Arrange with a local store or hobbyists to take extra fish before the tank overflows.

What fish can live with guppies?

Good tank mates are peaceful and similar in size: platies, mollies, corydoras, small tetras that are not fin-nippers, otocinclus and snails. Avoid fin-nippers (some barbs), large cichlids and any fish big enough to eat them. Male bettas and guppies are a risky mix. And keep guppies away from goldfish, which prefer cooler water and can swallow small fish.

What are common guppy health problems?

Sign	Possible cause	First steps
Clamped fins, lethargy	Poor water quality, cold	Test water, check heater
Frayed tails	Fin rot, fin-nipping tank mates	Clean water, review tank mates
White spots	Ich parasites	Consult a fish veterinarian or experienced store
Gasping at surface	Ammonia/nitrite, low oxygen	Test, partial water change, add surface agitation
Bent spine in adults	Age, genetics, injury	Monitor; isolate if declining

The Merck Veterinary Manual calls poor water quality the most common cause of environmental disease in fish. Quarantining new fish — as UF/IFAS Extension recommends for all new animals and plants — prevents many outbreaks that come in with new purchases.

How do I choose healthy guppies at the store?

Many guppy problems arrive with the fish, so a few minutes of observation before buying pays off:

Watch the whole tank, not just the fish you like. Avoid tanks with dead or gasping fish, even if your chosen fish look fine.
Look for open fins and active swimming. Clamped fins, hiding in a corner or hanging at the surface are warning signs.
Check the body. Avoid fish with white spots, cottony patches, sunken bellies, bent spines or frayed tails.
Ask questions. UF/IFAS Extension notes many aquarists don’t get complete information unless they ask — about origin, how long the fish have been in the store, and what they are being fed.
Buy the sexes you want. Ask staff to net only males if you don’t want fry, and remember females from mixed tanks are likely already pregnant.

At home, float the bag to match temperature, mix in small amounts of tank water over 20–30 minutes and net the fish into the tank. A separate quarantine tank for two to four weeks is the best protection for an established group.

What about fancy guppy strains?

Selective breeding has produced dozens of tail shapes and color strains — delta, fantail, lyretail, cobra, tuxedo and more. Fancy strains are often more delicate than wild-type or “feeder” guppies, especially in long-finned males that swim less efficiently. Give them gentle flow, very clean water and peaceful tank mates, and avoid mixing strains if you want to keep their traits in your fry.

If you breed guppies for several generations from a small group, inbreeding can show up as smaller fish, weaker fry or more deformities. Hobby breeders avoid this by adding unrelated fish of the same strain every so often, after quarantine, and by selecting only the healthiest, best-shaped fish to breed. Culling decisions and rehoming extra fish should always be planned before a colony grows too large.

Common guppy mistakes

Buying only females or a mixed group without a plan. Guppies breed readily, and females can store sperm. Decide early whether you will keep males only, raise fry, or have a plan to rehome the extras.
Keeping too few females per male. A single female with several males is chased constantly. Follow the ratio guidance above.
Housing guppies with fin nippers. Long-finned males are easy targets for nippy fish. Check the temperament of any tank mate before buying it.
Skipping hiding places. Dense plants and floating cover give fry and stressed females somewhere to escape.
Overstocking as the population grows. A tank that started at a comfortable number can become crowded within a few generations. Test the water more often as numbers rise and rehome fish before quality slips.
Ignoring the first signs of illness. Clamped fins, white spots or a fish hanging at the surface are worth acting on right away, before the problem spreads.

Guppy care checklist

Cycled, heated tank of 10+ gallons with gentle filtration and a lid.
74–80°F, pH around 7.0–8.0, ammonia and nitrite at zero.
Small meals once or twice a day.
Sensible sex ratio — or a plan for fry.
Weekly 25% water changes.
Never release guppies outdoors.

Want to go further with fish that feed plants? See aquaponics for beginners.