Guppy

Quick facts

Adult size

5 cm

Lifespan

can live up to 4 years; captive average 1.5-2.5 years; fancy strains often shorter

Tank zone

top

Temperament

peaceful

Difficulty

beginner

Water parameters

Temperature

22–28°C

pH

7.0 to 8.0

Hardness

8 to 25 dGH

Tank requirements

Minimum volume

40 L

Minimum length

50 cm

Flow

low

Lighting

moderate

Substrate

any

Hiding spots

needed

Feeding

Diet: omnivore, feeds primarily at the surface.

Omnivore that eats anything: flake food, micro pellets, frozen bloodworm, frozen brine shrimp, frozen daphnia, blanched peas, blanched zucchini, algae, biofilm. Not picky, not slow, always hungry. Feed twice daily in small amounts. Color-enhancing food with spirulina, astaxanthin, or carotenoids improves the vibrancy of red, orange, and yellow coloring in males. Newly born fry eat crushed flake and baby brine shrimp from day one. Overfeeding is easy because guppies always act hungry; restrain the impulse.

Compatibility

• The classic beginner livebearer. Peaceful, colorful, and breeds in any container of water that's vaguely tropical. The challenge isn't keeping guppies alive; it's preventing population explosion.
• Males have long, flowing fins that attract fin-nippers. Avoid housing with tiger barbs, serpae tetras, and other known nippers. Even mildly nippy species target guppy tails because the waving display fins trigger a chasing response.
• Keep in a ratio of 2-3 females per male. A single female with multiple males gets harassed constantly and will die from stress. An all-male tank avoids breeding but some males redirect aggression toward each other's fins.
• Hybridizes with endler's livebearers (Poecilia wingei) because they're closely related or possibly the same species. If keeping both, house them separately or accept that offspring will be hybrids.

Habitat

Originally native to northeast South America (Venezuela, Trinidad, Barbados, and northern Brazil) but now found on every continent except Antarctica due to deliberate introductions for mosquito control. Established feral populations exist throughout tropical and subtropical regions worldwide. The species is arguably the most widely distributed tropical freshwater fish on Earth. Guppies have been in the aquarium hobby since the late 1800s. The fancy strains available today bear almost no resemblance to wild-type fish: selective breeding has produced enormous fantails, swordtails, and delta-tails in every color combination imaginable. Wild guppies are small (males 3 cm, females 5 cm) with modest coloring. Fancy males reach 5–6 cm with tails that double the body length. The species is a model organism in evolutionary biology; guppy adaptation to predation pressure, sexual selection, and color pattern evolution has been studied intensively in Trinidadian populations. All hobby stock is tank-bred. Prices range from near-free (feeder guppies) to $50+ for rare fancy strains.

Breeding

Livebearer that breeds without any intervention from the keeper. Males have a modified anal fin (gonopodium) that transfers sperm directly to the female. Females store sperm and can produce multiple broods from a single mating, which is why a single purchased female can populate a tank on her own. Gestation is 21-30 days. Females give birth to 10-60 fully formed, swimming fry every 4-6 weeks. Fry are small but functional from birth and eat crushed flake, baby brine shrimp, and micro food immediately. In a community tank, most fry are eaten by adults (including the mother). In a dedicated breeding tank or with enough dense cover (floating plants, moss mats), survival rates increase dramatically. Selective breeding for specific traits (tail shape, color pattern, body shape) is a deep hobby-within-a-hobby with dedicated guppy breeders maintaining dozens of strains. The genetics of guppy coloring are complex, involving sex-linked genes, autosomal genes, and interactions between them. Understanding guppy genetics well enough to predict offspring is a multi-year learning curve.

Common problems

Fancy guppies from mass-breeding farms are genetically weakened by decades of intensive inbreeding. The fish sold in chain pet stores are fragile compared to wild-type guppies or well-maintained breeder lines. Common issues: columnaris (a bacterial infection showing as white patches or eroded fins), internal parasites (wasting despite eating), and swim bladder problems (fish floating sideways or sinking). "Guppy plague" is a term used by hobbyists for the pattern where new guppies die one by one over 2-4 weeks after purchase. The cause is usually a combination of farm-bred fragility, transport stress, and parameter differences between the store and the home tank. Buying from local breeders instead of chain stores dramatically improves survival. Fin rot in males targets the elaborate tails; a torn or rotting fantail is both a health problem and a loss of the fish's main visual appeal. Keep water quality high to prevent it. Wild-type and endler-cross guppies are vastly hardier than fancy strains if the priority is survivability over appearance.

Bioload

Bioload coefficient: 1.0 (small body but constant feeding and prolific fry production keeps bioload at ~neon equivalent).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size