West African River Biotope Aquarium

A soft, acidic West African river biotope drawn from the Congo and Niger basins: Pelvicachromis, Congo tetras, Aphyosemion killifish and butterflyfish, leaf litter, wood and subdued light.

The rivers: Congo and Niger basins

The Congo is the deepest river recorded, with measured depths of about 220 m, and its full system runs 4,700 km through a basin of 4,014,500 km² shared by ten countries; the Democratic Republic of Congo holds 62.16 percent of that area (Wikipedia). It flows through the Congo rainforest, the second-largest rainforest on Earth, and receives large tributaries such as the Ubangi, the Sangha and the Kasai. Almost 800 fish species are recorded from the basin, more than 300 of them at the Livingstone Falls alone, with roughly 80 endemics there, and the Kasai sub-basin holds over 200 species of which about a quarter are endemic. Average discharge at the mouth is 41,000 m³/s.

The Niger, 4,200 km long with a basin of about 2.1–2.3 million km² across Guinea, Mali, Niger, Benin and Nigeria, is a comparatively clear river that carries only a tenth as much sediment as the Nile because its headwaters lie on ancient rock (Wikipedia). It floods every year from September, peaking in November and receding by May, and its Inner Delta swells from 3,900 km² in the dry season to about 20,000 km² in the wet season. The aquarium biotope modelled here is not the main channel of either river but the small, shaded forest streams, creeks and swamp margins of the lower Niger, coastal Cameroon, Gabon and the Congo drainage where the dwarf cichlids, tetras and killifishes of the trade actually live.

Soft, acidic water and leaf litter

Wild Pelvicachromis pulcher in southern Nigeria and coastal Cameroon live at 24–26 °C, pH 5.6–6.2 and a hardness of only 12–22 mg/L CaCO3, in both slow and fast-moving water but only where patches of dense vegetation exist (Wikipedia). FishBase gives the species a broader pH range of 5.0–8.0 and 5–19 dH and records it in both fresh and brackish water. Aphyosemion striatum comes from shaded perennial lowland rainforest streams, pools and freshwater swamps between Equatorial Guinea and the lower Ogooué in Gabon (Seriously Fish). Pantodon buchholzi occupies slow-moving and still creeks, lakes and swamps under dense or overhanging vegetation, in water preferably stained with tannins (Seriously Fish). Leaf litter beds form where the current slows, on the inner side of meanders, and aquatic fungi break down the leaves so that detritivores can use them; Tannin Aquatics notes that these beds are among the richest tropical freshwater niches and suggests a practical upper limit of 15–30 cm (6–12 in) of litter in an aquarium.

Typical fauna

• Pelvicachromis pulcher — eastern Benin, southern Nigeria and western Cameroon; maximum 11 cm TL; cave-spawning pair-bonding cichlid; IUCN Red List: Least Concern (2019, FishBase).
• Phenacogrammus interruptus — endemic to parts of the Congo drainage in the Democratic Republic of Congo; a schooling omnivore that takes worms, insects, crustaceans, algae and zooplankton (Seriously Fish).
• Aphyosemion striatum — a killifish of Gabon and Equatorial Guinea; one of 100 recognised Aphyosemion species (Wikipedia, Seriously Fish).
• Pantodon buchholzi — surface-dwelling insectivore of West and Central Africa, recorded from Sierra Leone and Nigeria to the Congo basin (Seriously Fish).
• Companions named by Seriously Fish for this community: Synodontis catfishes, Corydoras, small characins and barbs, and other dwarf West African cichlids where space allows.

Published aquarium ranges

The ranges below are from Seriously Fish species profiles. Congo tetras want water on the acidic side of neutral, soft and with good circulation; the butterflyfish wants minimal water movement, so a shared tank uses gentle, diffuse return flow rather than a jet.

• Pelvicachromis pulcher: 24–27 °C, pH 5.0–7.5, 0–12 dGH; captive-bred fish are more adaptable than wild ones.
• Phenacogrammus interruptus: 23–28 °C, pH 6.0–7.5, 3–18 dGH.
• Aphyosemion striatum: 20–26 °C, pH 6.5–7.5, 3–12 dGH.
• Pantodon buchholzi: 23–30 °C, pH 6.0–7.5, 5–15 dGH.

Layout: wood, litter, caves and subdued light

A sand or fine gravel bed is used because Pelvicachromis excavate when breeding, and wild fish dig their shelters under plants (Seriously Fish, Wikipedia). Driftwood branches and roots, several caves and a dark substrate provide the cover all four species seek. Floating plants diffuse the light: Seriously Fish recommends them for the Congo tetra, the killifish and the butterflyfish, together with dim lighting, and names Anubias among the plants for an African biotope with driftwood. A layer of dried leaves in the quiet zones reproduces the litter beds; it releases tannins that tint the water, so it should be added stepwise while pH is monitored. The open middle water is left for the tetra school, the surface for the butterflyfish, and the floor and caves for the cichlid pair.

Feeding and behaviour

Wild Pelvicachromis pulcher feed largely on diatoms, green algae, plant fragments and blue-green algae, with invertebrates a minor part of the diet (Wikipedia); in the aquarium a cichlid pellet is supplemented with live and frozen foods. The species is monogamous and lays 40–100 adhesive eggs in a cave (Wikipedia; Seriously Fish cites up to 300), with brood care lasting 21–28 days and fry free-swimming after 7–8 days. Pairs become territorial when breeding. Phenacogrammus interruptus is kept as a mixed-sex shoal on a base of at least 120 × 30 cm and should not be housed with fin-nippers. Aphyosemion striatum is peaceful and shy, feeds on small live or frozen foods such as Daphnia, and deposits 20–30 eggs a day for about two weeks; eggs hatch in 10–14 days in water. Pantodon buchholzi feeds only at the surface on insects and frozen invertebrates and needs a base of 90 × 30 cm.