A. calvus is a predator by nature and its body shape has been adapted to allow it to enter small crevices and gaps in the rockwork of Lake Tanganyika to prey on eggs, fry and small fish. Its laterally compressed shape makes the fish hard to spot head on, giving it an advantage over would be predators and prey alike. It is also quite well-armoured, possessing thick scales which can be turned towards potential attackers. These can cause real damage with their serrated edges.

Several colour form…

This species was first imported for the aquarium hobby during the 1950s and was for many years misidentified and traded as Bedotia geayi, a valid, but different-looking congener native to the Mananjary River system, south of the range of B. madagascarensis. In terms of external characters, the two are most easily told apart by differences in colour pattern, particularly that of the unpaired fins, and some morphometric counts.

Perhaps looks best in a heavily-planted set-up or natural-style arrangement comprising a sandy substrate plus some driftwood roots and branches.

The addition of dried leaf litter would further emphasise the natural feel and as well as offering additional cover for the fish brings with it the growth of microbe colonies as decomposition occurs.

These can provide a valuable secondary food source for fry and the humic su…

The majority of original populations have already been extirpated due to introduction of invasive species such as Gambusia holbrooki and Poecilia reticulata, ongoing deforestation of the Ambohitra Massif, and physical diversion of the source of the Sakaramy River for domestic use by locals.

An additional population may exist in a stream on the southern slope of the Ambohitra Massif on the road between Bobasokoa and Anivorano, near the village of Andranotohiliny, but this requires verification.

Type locality is given simply as ‘Seychelles’ and this species was originally endemic to the Granitic Seychelles, i.e., those islands in the centre of the group composed chiefly of granite rock.

A translocated population now exists on Zanzibar while in the Seychelles it’s known from the islands of Mahé, Praslin, Silhouette and La Digue.

For a number of decades this species was thought to occur throughout much of Madagsacar’s western slope but populations immediately to the north and south of the range described above (see ‘Distribution’) are currently considered to represent unidentified species, while a number of populations from the Mahavavy du Sud and Betsiboka riv…

Described from close to the city of Beira, Mozambique and for many years thought widely-distributed between the Kruger National Park, South Africa to the Kwa-Kwa River north of the Zambezi delta.

Populations from the south and north of this range exhibiting differences in colour pattern and morphology have now been described as N. pienaari and N. krysanovi, respectively, meaning N. rachovii sensu stricto is restricted to the area between the lower Pungwe and Zambezi river basins in eastern Mozambique.

Inhabits ephemeral, water-filled depressions, pools and swamps mostly located in lowland floodplains. Water levels in these seasonally-variable habitats typically decrease during the dry season and eventually become completely dessicated for several months each year.

Near Bagamoyo it’s been collected from pools of a flat, grassy floodplain alongside the congeners N. annectens, N. janpapi and N. melanospilus, while at Soga it occus together with N. janpapi and N. ocellatus. Most habitats appear to be heavily overgrown with terrestrial vegetation.

Type locality is ‘Rufiji River near Utete, eastern Tanzania’, and this species is apparently endemic to the lower Rufiji including the Selous Game Reserve and freshwater parts of the Rufiji delta region.

Populations in the aquarium hobby include ‘Rufiji river camp’, ‘Kikongono’, ‘Ruhoi River’, ‘Kanga’, ‘Utete’, ‘Saadani Game Reserve’, ‘Ruvu River’, ‘Bagamoyo’, ‘Makurunge’, ‘Killimani’, ‘Chamakwese’, ‘Nyamwage’, ‘Mohoro’, and ‘Ukuni’.

There exist many different populations of this species in nature, some of which are now threatened or extinct, due to rapid human development in Ghana and the Ivory Coast in recent years. It is not a common fish in the hobby. Interestingly, it appears that F. walkeri occurs as both an annual and non-annual fish. This adaptation allows it to inhabit many different habitats, as it is able to breed in both permananent and temporary bodies of water.
Note that this fish prefers cooler temperatures t…