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Steatocranus

The Genus Steatocranus

Introduction

Steatocranus are an interesting group of fishes from a small genus comprising of nine species of rheophilic (living in flowing water) African cichlids. This genus is a personal favourite of mine ever since seeing my first photo of Steatocranus casuarius many years ago. All Steatocranus have reduced swim bladders which helps them to sink to the bottom and shelter among the stones which prevent them from being swept away without having to use up energy swimming against the flow of the river. They peck at the stones for algae and invertebrates as well as taking other food when the opportunity arises. In the aquarium they have very strong characters which stands them apart from a lot of other aquarium fishes and although they may squabble among themselves they are all fairly peaceful providing that they have enough space and they are kept with the right tank mates.

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Steatocranus casuarius, photo by author

The Genus of Steatocranus

The nine species are:

  • Steatocranus bleheri Meyer, 1993.
    Size – 6 – 8cm (2.2 – 3.2 in), Wild status – data deficient.
    Breeding – Cave spawner. Wild diet – opportunistic omnivore.
    Range – The upper Kafubu River basin, Luapula River System, Shaba,
    Democratic Republic of the Congo.
  • Steatocranus casuarius Poll, 1939.
    Size – 10cm (4in) females smaller than males, Wild status – least concern.
    Breeding – cave spawner. Wild diet – mainly algae.
    Range – The rapids on the Lower Congo River.
    Democratic Republic of the Congo.
  • Steatocranus gibbiceps Boulenger, 1899.
    Size – 10cm (4in), Wild status – least concern.
    Breeding – cave spawner. Wild diet – mainly gastropods.
    Range – The rapids on the Lower Congo River.
    Democratic Republic of the Congo.
  • Steatocranus glaber Roberts & Stewart, 1976.
    Size – 5.3cm (2in), Wild status – vulnerable.
    Breeding – cave spawner. Wild diet – diatoms.
    Range – only known from one location near Inga Dam site.
    Democratic Republic of the Congo.
  • Steatocranus irvinei (Trewavas, 1943).
    Size – 11cm (4.5in), Wild status – near threatened.
    Breeding – cave spawner (prolific). Wild diet –  aufwuchs
    Range – endemic to the Volta River system.
    Burkina Faso; Ghana.
  • Steatocranus mpozoensis Roberts & Stewart, 1976.
    Size – 5.5cm (2.2 in), Wild status – data deficient.
    Breeding – cave spawner? Wild diet – omnivore.
    Range –  is only known from the mouth of the Mpozo River and the opposite bank in the main river, Lower Congo River basin.
    The Democratic Republic of the Congo.
  • Steatocranus rouxi (Pellegrin, 1928).
    Size – 6cm (2.5in), Wild status – data deficient.
    Breeding – cave spawner. Wild diet – omnivore.
    Range – is only known from the type locality in the vicinity of Luluabourg, in the rapids of the Lulua River but it may be more widespread.
    The Democratic Republic of the Congo.
  • Steatocranus tinanti (Poll, 1939). Under revision, maybe a species complex.
    Size – 6.3cm (2.6in), Wild status – least concern.
    Breeding – cave spawner. Wild diet – omnivore
    Range – rapids of Pool Malebo (Stanley Pool) and the Lower Congo River.
    The Democratic Republic of the Congo.
  • Steatocranus ubanguiensis Roberts & Stewart, 1976.
    Size – 5.3cm (2.2in), Wild status – data deficient.
    Breeding – cave spawner. Wild diet – omnivore.
    Range –  is only known from the type locality: Mbomou river, a tributary of the Ubangui river but maybe more widespread.
    Central African Republic

Steatocranus casuarius is probably the most commonly kept species of these along with Steatocranus tinanti and Steatocranus irvinei.

Aquarium care

General: For an adult pair the minimum recommended tank size is 70 – 100 litres, or around 36 x 15 x 12. Good water movement is very helpful with these fishes because it recreates their natural environment and helps to keep the water highly oxygenated. They live in quieter eddies in generally fast flowing water so don’t try to create to much turbulence, good circulation is far more natural.
Steatocranus are relatively unfussy about their water chemistry which should be fairly neutral and medium hard, pH 6 to 8 and a temperature between 24-28°C (75-82°F) will suit them very well. Most importantly there water must be high quality, high in dissolved oxygen and low in pollutants such as organic waste, urea and nitrogenous compounds. A good regime of partial water changes is required to maintain water quality.

Despite their large mouths and quite an aggressive appearance they tend only to squabble among themselves mostly ignoring other fishes. If their aquarium is large enough Steatocranus can be kept in groups in a community tank with suitable tank mates such as medium sized African tetras.

Feeding: All Steatocranus are omnivores which means they eat a wide variety of food which includes both meaty and vegetable matter. Most species favour vegetable matter with the exception of S gibbiceps. which has a short intestine indicating a more carnivorous preference. In captivity they will browse any algae and accept a wide range of aquarium prepared food which should be supplemented with some live or frozen food and some fresh greens.

Breeding: All Steatocranus are cave spawners and most are quite prolific when they are well cared for. The ideal way to begin breeding these fish is to buy a small group of six or more unrelated juveniles. The unrelated part is important in order to avoid inbreeding, for example if you purchased a group of siblings from a breeder and went on to breed them and then someone else comes along and buys a group of those fry in order to obtain a breeding group of their own you can see how quickly problems due to inbreeding could begin to show. Having bought a group of unrelated fish with the intention of breeding from them it would be better to keep them in a species tank. Let nature take its course, pairs will form once the fish begin to mature at which stage you could maintain a pair in their own aquarium or keep them as a group if the aquarium is large enough to allow each pair sufficient space to hold a territory. The aquarium should be set up with numerous caves.
Being cichlids they require no spawning triggers other than being well cared for.
A pair will select an existing cave or they may choose to make their own by digging under a stone, this is where they will lay between 20 to 120 eggs which hatch after about one week and the fry become free swimming another week later, although the time it takes is temperature dependent and it may be a little faster or a little slower than this. Once free swimming the fry are large enough to take newly hatched brine shrimps, micro worms, hard boiled egg yolk or even finely powdered flake food.
Steatocranus are generally very good parents, when protecting their brood they will very aggressively defend their territory and any straying fry are rounded up and quickly returned to the main shoal of fry. Parental care can last for eight weeks or more and even if the parent fish produce a new brood the older juveniles are still well tolerated with the territory of the parents.

Aquascape: Being fish from rapidly flowing water their natural environment consists of water worn stones of varying size which form natural caves as they lay next to or on top of each other. No plants grow in their natural environment. To see the fish as they would look in their natural habitat try to create a river bed look to their tank. This isn’t of course an essential but they do need access to some sort of caves if they are to behave and breed naturally.

Steatocranus

A river bed tank with good water movement using a spray bar makes the ideal home for Steatocranus spp.
Photo by author

About Andy Rapson

I've been interested in fish for about fifty years and I have kept many different species in that time. I have also worked in the fish trade running my own fish shop and I'm a Fishbase collaborator. I'm now mainly interested in fish husbandry, fish health, native marines and fish photography.

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