Breeding Mosaic Guppy

How to breed the Mosaic Guppy strain of Poecilia reticulata: a livebearer dropping live fry; line-bred for the heritable mosaic-patterned tail of mixed colour patches.

Overview

The Mosaic Guppy is a selectively bred strain of Poecilia reticulata with a mosaic-patterned tail made up of mixed colour patches. Like all guppies it is a livebearer with internal fertilisation, and reproduction is very straightforward, requiring no special effort.

Sexing

Males are smaller (about 1.5-4 cm) and more colourful, and possess a stick-like modified anal fin called the gonopodium used to transfer sperm. Females are larger (about 3-7 cm), plumper and duller, and a pregnant female shows a dark gravid spot behind the anal fin.

Conditioning

Maintain several females per male, since males pursue females constantly. To preserve the mosaic tail pattern, breeders line-breed selected stock: the fancy colours and patterns are heritable, with colour genes largely Y-chromosome linked, so pairing well-marked parents propagates the strain.

Birth & Fry Care

Gestation typically takes about 4-6 weeks (roughly 20-60 days at 25-27.8 degrees C), after which the female drops live, free-swimming fry. A brood may number from a few to around 100 young, with broods often between 30 and 60. Note that females can store sperm and continue producing broods for six months or more even without a male present.

Common Challenges

Adult fish will eat the fry, so dense planting with floating vegetation gives the young shelter, or the fry can be moved to a separate tank for higher survival. Fry take live foods such as brine shrimp and reach maturity in roughly three to four months.