Oreochromis mossambicus

Mozambique Mouthbrooder

Classification

Cichlidae

Distribution

Native to the East African coast, specifically Mozambique, Lesotho, Botswana, Swaziland, Zimbabwe and Malawi. However, escaped populations now exist in over 90 countries with the fish initially having been imported for aquaculture.

Habitat

An incredibly adaptable species that is found in rivers, streams, ponds, lakes and coastal plains in it’s native range. It occurs in both fresh and brackish waters and usually inhabits shallow areas.

Maximum Standard Length

15.6″ (39cm).

Aquarium SizeTop ↑

80″ x 24″ x 24″ (210cm x 60cm x 60cm) – 760 litres for adult fish. Juveniles can be grown on in smaller aquaria.

Maintenance

Not critical. A sandy substrate is best. Plants should not be used, as they will be eaten. A large, efficient filtration system is essential as this species is very messy. Otherwise, decor is down to personal preference.

Water Conditions

Temperature: 70-81°F (21-27°C)

pH: 6.2-8.5

Hardness: 10-30°H

Diet

Very unfussy and will eat most foods offered. Some vegetable matter should be included in the diet.

Behaviour and CompatibilityTop ↑

A very robust species that is territorial when spawning but is otherwise quite peaceful. Obviously, an enormous tank is needed to keep it in a community situation. It can be combined successfully with large African and Central American cichlids, Loricariids, Synodontis sp. etc. Small fish will be eaten. If kept with others of it’s own species, they will squabble amongst themselves but rarely is any real damage done unless breeding occurs.

Sexual Dimorphism

In the natural form, males take on heightened colours during spawning and mature males often have a thicker upper lip and dorsal fin. Males also tend to be slightly larger than females.

Reproduction

Easy. Maternal mouthbrooder. We recommend the purchase of 5 or 6 youngsters and allowing them to pair up naturally. Obviously, a massive tank is required but water parameters are less important. Aim for a temperature of 75°F and a pH of around 7.0 and you will be fine. Sand is the preferred substrate.

Spawning is initiated by the male, who excavates a pit in the substrate to act as the spawning site. He will then guard this area fiercely and attempt to entice females to mate with him. A willing female lays her eggs directly onto the substrate of the spawning pit and allows the male to fertilise them before taking them into her mouth. The male now plays no further part in broodcare and the female does not remain in his territory.

The female will carry the brood for around 14 days before releasing the free swimming fry. Generally, she will not eat during this period and can easily be spotted by her distended buccal cavity. Following release of the fry, broodcare by the female lasts for another week or so, with the fry seeking refuge in her mouth if threatened or distressed. She will actually signal to the fry to enter her mouth if she senses danger by quickly darkening parts of her face.

The fry grow very quickly indeed and are sexually mature at only 8 or 9 months of age. They can be fed on brine shrimp nauplii or powdered flake food from the day they become free swimming.

NotesTop ↑

One of the most invasive fish species in the world, O. mossambicus is one of the species farmed for supermarkets and restaurants across the globe. Several colour varieties have been selectively bred from the natural green fish to make the fish more appealing to consumers and unsurprisingly, it is these more brightly coloured forms which are usually seen in aquaria. Some of these variants are cross breeds with other species of Oreochromis.

The destructive effect of O. mossambicus on non-native ecosystems into which it escapes or is released is mainly due to it’s adaptibility. It has been recorded over a temperature range of 60-110°F and in water varying from pure freshwater to full marine conditions. It is often described as an “aquatic dustbin” as it eats virtually anything and it breeds under almost any conditions, even when food is scarce. The broods themselves number several hundred and a single female can produce 3 or 4 a year.

Known commonly in the aquarium trade as the “Mossie”, O. mossambicus does not make a particularly good aquarium fish either. It has a large adult size, a messy nature and is not especially attractive, nor does it exhibit any particularly interesting behaviour. The ease with which the fish breeds, and resultant large broods of swiftly growing fry can also spell trouble as the young are not at all popular with dealers and other hobbyists. However, it is still regularly seen for sale (though thankfully not as often as it once was), and it is many an unsuspecting fishkeeper who has purchased a cheap, cute 1″ pink cichlid only to find he or she has a monster on their hands only a few months later. Although it is very easy to keep and breed, it is not recommended to the vast majority of hobbyists.