Poecilia reticulata (guppy)

Complete Technical Profile

🐠 Common name

Guppy, Million Fish, Rainbow Fish

🔄 Synonyms

Lebistes reticulatus (obsolete), Poecilia wingei (for Endler), Fancy Guppy (in the trade)

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🔬 Morphology

• Elongated body, slightly compressed laterally
• Dorsal fin developed in ornamental males
• Wide caudal fin, with lyre, triangle, veil and delta variations
• Mouth turned slightly upwards (surface feeding)

🔎 How to recognise this fish?

• Small size
• Brilliant colouring (in the males)
• Wide and variable fins
• Extreme liveliness in the tank

♂♀ Differences between males and females

Characteristic	Male	Female
Size	2.5 – 3.5 cm	4 – 6 cm
Colours	Very lively, brilliant	More sober, sometimes matt
Gonopodium	Present (modified anal fin)	Absent
Caudal fin	Wide and decorative	Shorter

🌗 Way of life

Diurnal. Active during the hours of light, exploratory and sociable.

🗺 Territoriality

No, not territorial. It lives in groups, with a slight hierarchy among the males (reproductive competition).

⌛ Life expectancy

1.5 – 2.5 years in the aquarium (up to 3 years in excellent conditions).

📏 Maximum size in nature

Males: 3 – 3.5 cm. Females: up to 6 cm.

📐 Maximum size in the aquarium

The same size as the wild form. In some selected varieties the fins can exceed the body.

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🧬 Description

The guppy is a small South American ovoviviparous fish, known for its phenotypic variability, its extraordinary reproductive capacity and its symbolic value in aquarium popularisation. It is used in genetics, ethology and as an ecological ally in the fight against mosquitoes.

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🌎 Distribution

Native to: north-east South America, Trinidad, Barbados Introduced in more than 60 tropical countries for sanitary and ornamental purposes

❗ STATUS ON THE IUCN RED LIST

LC (Least Concern) – Not threatened. Source: IUCN Red List

🏞 Habitat (origin and distribution)

• Streams, brooks, canals, stagnant or low-current waters
• Also urban or altered environments
• Frequent in warm and vegetated waters

🌡 Temperature in nature

22 °C – 28 °C

💧 pH value in nature

6.5 – 7.8

💦 Water values in nature

Fresh waters, moderately hard (GH 8-16), variable KH

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🐟 Keeping in the aquarium

🏠 Minimum dimensions of the aquarium

• 60 cm / 54 net litres for a basic group
• Recommended minimum group: 6 specimens (1 male for every 2-3 females)

🤝 Behaviour and compatibility

• Peaceful, sociable, suited to communities
• Avoid coexistence with fin-nipping fish (e.g. Puntius tetrazona)

💧 Recommended water values in the aquarium

Parameter	Ideal range
Temperature	23-26 °C
pH	6.8 – 7.8
GH	8 – 12 °dGH
KH	4 – 8 °dKH
Current	Weak – moderate

👥 Minimum population in the aquarium

Minimum 5-6 individuals. Ideal: 1 male for every 2-3 females in order to reduce stress.

🍽 Feeding

• Omnivorous: micro-invertebrates, algae, detritus
• In the aquarium: flakes, micro-granules, spirulina, artemia, daphnia, vegetable pastes
• It needs a varied diet rich in pigments in order to maintain colours and fertility

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❤️ Reproductive behaviour

• Active and continuous courtship on the part of the males
• Rapid copulation, thanks to the gonopodium
• The females can store sperm for several fertilisations

♀♂ Sexual dimorphism

• Males small, coloured, with a gonopodium
• Females large, round, with a short caudal fin and a visible gravid spot

🐣 Reproduction

• Ovoviviparous
• Gestation: 25-35 days
• Number of fry: 20-100 (depending on the size and the age)
• Frequency: about every 4 weeks

🛡 Protection of the fry

• In nature: shelter among floating plants
• In the aquarium: a nursery or dense plants (mosses, Ceratophyllum, Limnobium)
• Intra-specific predation frequent

🧬 Risks of hybridisation

• Possible crosses with Poecilia wingei (Endler): they produce fertile but unstable hybrids
• Uncontrolled crosses = loss of genetic lines

💪 Hardiness

A rustic, adaptable species, ideal for newcomers. Sensitive only to strong temperature swings and high nitrates.

💡 Lighting in the aquarium

• Medium intensity
• It brings out the colours in the males and stimulates exploratory behaviour

🌿 Recommended plants

• Limnobium, Pistia, Ceratophyllum, Elodea, Cryptocoryne, mosses
• They offer shelter and stimulate natural behaviour

🪨 Ideal substrate

• Fine sand or siliceous gravel
• They do not need a fertile substrate (but it is useful for rooting plants)

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🛍 Availability in the trade

Wide. Present in every aquarium shop. Obtainable in numerous ornamental varieties, from mass breeding or genetic selection (show guppy).

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✅ PROS

• Inexpensive, widespread, hardy
• Variety of colours and shapes
• Simple reproduction
• Compatible with community aquariums

❌ CONS

• Predation of the fry
• Males insistent with the females
• Possible diseases in selected subjects
• Risk of accidental hybridisation

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📦 Information boxes

📌 Endler vs Guppy: watch out for hybridisation

Poecilia wingei (Endler) and Poecilia reticulata can mate with each other, generating fertile hybrids. In the aquarium it is best not to mix them, if one wishes to maintain pure lines and selected reproductions.

🌿 The guppy is an excellent natural ally

In some tropical regions, the guppy is employed in canals to contain mosquito larvae (Aedes aegypti) thanks to its natural predatory behaviour.

🧬 Watch out for genetic selection

Ornamental varieties (e.g. show guppies) can have a reduced resistance to diseases. Hybrid lines or lines derived from close crosses can show fragility.

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❓ FAQ – Frequently asked questions

🐟 Can the guppy live on its own?

Technically yes, but it is not advisable. It is a gregarious fish and it must be kept in groups of at least 3-5 specimens, preferably with a ratio of 1 male for every 2-3 females.

🌡️ What is the ideal temperature for guppies?

Between 23 and 26 °C for bred varieties; the wild forms can tolerate wider swings as well.

🤝 Is the guppy compatible with other fish?

Yes, provided they are not too aggressive or predatory. Excellent companions are neons, corydoras, danios, platies, mollies, otocinclus.

🧪 Do guppies tolerate hard water?

Yes, they are very adaptable. However, the ideal values are pH 6.8–7.8, GH 8–20, KH 5–12.

🧬 How to avoid hybridisation with Endler?

Do not put Poecilia wingei and Poecilia reticulata in the same aquarium if you want to avoid crosses. The hybrids are fertile but not always genetically stable.

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📚 Glossary

• Ovoviviparous: organism that produces eggs which hatch inside the mother’s body, giving birth to already formed fry.
• Sexual dimorphism: evident differences between males and females of the same species.
• Fry: juvenile stage of a fish, immediately after birth or hatching.
• Endler (Poecilia wingei): species closely related to the guppy, smaller, with lively natural colourings.
• Linebreeding: genetic selection between related subjects in order to fix characteristics (risk of inbreeding).
• Community aquarium: tank populated by several different but compatible species.
• Sandy substrate: fine substrate recommended in order to avoid damage to the fins and in order to house rooting plants.
• Hardy fish: hardy species, suitable for beginners as well.