Leopardfish, Phalloceros caudimaculatus


Nathan Hill spotlights an attractive livebearer that's easy to keep and breed, and makes a far hardier alternative to the often problematic Dalmatian molly.

Common name: Leopardfish
Scientific name: Phalloceros caudimaculatus.
Synonyms: Girardinus caudimaculatus.

Size: Males reach a little over 3cm/1.2”. females typically to 6cm/2.4” but have been known closer to 7.5cm/3”.

Distribution: Native to South America, from Brazil to Uruguay and Argentina. It has also been introduced in an attempt to control numbers of mosquitos in Australia and Ethiopia where it now proliferates.

Diet: Like many small livebearers, this is an aufwuchs and algae grazer when not chasing small insects or crustacea from the bottom of its environment. In the aquarium it can turn to plants, damaging softer leaves.

It will happily accept most offered foods, although use plant-heavy dried foods to maintain colours and vigour.

Water: Incredibly tolerant of many parameters, this fish seems unfazed at pH values between 7.0 and 8.0, although in their native range 7.4 to 7.6 is the norm. Hardness values anywhere between 8 and 20° are accepted. Some keepers report increased success when using very low levels of salt.

Temperature: Anecdotal reports suggest these fish have survived in waters plummeting to 5°C/41°F. Records show fish caught from waters below 10°C/50°C, although their duration in these conditions is uncertain.

Conversely, they have been found in waters up to 35°C/95°F.

They can be considered subtropical, a tank of 15-20°C/59-68°F is optimal and an indoor, unheated aquarium will easily sustain them.

Habitat: Their natural range consists of slow, lagging rivers and streams, as well as ponds densely packed with weeds. They are even found in similar habitats in estuarine regions and have some degree of brackish tolerance.

Aquarium: Your aquarium should be heavily planted and have a fine gravel or sand substrate. Surface cover is preferred, with duckweed floating at the top of the tank.

Notes: The leopardfish is now considered a pest in some parts of the world where its introduction to eat mosquito larvae was a role in which it has spectacularly failed.

Although easy to breed, it is not a common import into the UK and will often need to be tracked down by the keen aquarist/breeder.

Breeding: This is easily achieved as the fish is a livebearer. Males can be sexed through the presence of the gonopodium and by their smaller, leaner size.

Try to keep three to five females for every male, as they have voracious reproductive appetites, and can pester solitary females.

Offspring numbers are linked to age of adults, with younger fish producing fewer young. Expect as low as ten fry for a young female, and up to 100 for a good-sized adult. The gestation period runs for an average of 24 days.

Some keepers panic when the offspring appear stillborn, as they will often drop to the tank bottom and remained curled up in the substrate for some time before moving.

Why we like it: The only realistic rival to the leopardfish’s markings is the Dalmatian molly. This latter fish is often in poor condition, emaciated, or the result of bad breeding lines, and tends to be problematic to keep. By contrast, Phallocerus are incredibly hardy and have none of the inherited genetic problems mollies can carry.

Availability: These fish were spotted at S and C Aquatics, County Durham.

Price: £4.99 each.

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