Guppy

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: any.

Behavior

Plant interaction: plant safe.

Feeding

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.

Origin and habitat

Native to Venezuela, Barbados, Trinidad, northern Brazil, and the Guyanas. Also recorded from Antigua and Barbuda and Suriname. First described by Wilhelm Peters in 1859 as Poecilia reticulata. Named after Robert John Lechmere Guppy (1836-1916), a British-born civil engineer and naturalist in Trinidad who sent specimens to the Natural History Museum in London. Günther named it Girardinus guppii in his honor in 1866. Widely introduced for mosquito control, but the IUCN's invasive species database reports rare to non-existing measurable effects on mosquito populations, with negative to perhaps neutral effects on native fishes. A key to invasive success: females store sperm in ovaries and gonoducts for up to eight months, meaning males are capable of posthumous reproduction. A single pregnant female can colonize a new waterway. Fancy guppy strains (veiltail, halfmoon, delta, sword, snakeskin, Moscow, dumbo ear) bear little resemblance to wild fish. Careful line breeding took off in the 20th century. Wild guppies are drab; vivid colors and flowing tails are products of selective breeding. Wild-water temperature range is 18–28°C.

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

Further reading

• Setting up a breeding tank