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The African oddballs
02 February 2018
Unusual fish to add interest to your community tank
The African fish fauna is extremely diverse, including large numbers of relatively primitive groups of fish, such as bichirs and mormyrids, living alongside things like cichlids that evolved, in geological terms at least, only yesterday. This wonderful variety of fish means that exports of fish from Africa invariably include many strange and unusual fish, commonly referred to as ‘oddballs’ in the fishkeeping hobby. Some make excellent community tank residents, and these are the focus of this article.
Before looking in detail at these African oddballs, it’s a good idea to remind ourselves of the golden rule of buying oddballs: never buy a fish you can’t positively identify. Sometimes the retailer will know the fish and can provide you with the essential information about water chemistry requirements, diet, social behaviour, and so on, but sometimes the fish will be as unknown to the staff as it is to you. If in doubt, pass on the fish until you can look it up in your favourite aquarium fish encyclopaedia or web site.
Oddballs are oddballs because they aren’t widely kept in aquaria, and that often implies that they have special needs that aren’t easy to accommodate. After all, the fishes that have become most widespread in the hobby are those that are peaceful, happy to eat flake, indifferent to water chemistry or quality, and easy to breed. In contrast, oddballs place particular demands on the aquarist. Sometimes this is no more difficult than providing the right sort of food; some species need a vegetable-based diet, for example. Other species are more challenging, needing perhaps a soft and acidic water conditions, or being too predatory to be compatible with smaller species.
However, adding an oddball to a community tank is a great way to make expand your fishkeeping experience, and many advanced aquarists move on to specialising in these fish as their skills develop. The following selection of fish includes some of the most widely traded oddballs that can work well in community tanks. None is especially difficult to keep, and any aquarist successful with things like angelfish and tetras should be able to manage these just fine.
Ropefish, Erpetoichthys calabaricus
The ropefish is an eel-like fish closely related to the bichirs (Polypterus spp.) and shares with them a distinctly prehistoric appearance. Like bichirs, it is obviously armour plated, and it is an obligate air-breather — this means it must be able to reach the surface of the aquarium to gulp air, otherwise it will drown. In the wild ropefish inhabit pools, ditches, and other sluggish waters, and being able the breathe air makes it much less sensitive to high temperatures and poor water quality that most other fish. Ropefish are somewhat amphibious, being able to slither through mud and wet vegetation between pools, and in aquaria they will certainly spend a great deal of time trying to escape, so a tightly-fitting lid is essential!
Unlike the bichirs, ropefish are peaceful, sociable species that will get on well with other fish. They are predatory though, and quickly eat small fish like neons or guppies, but larger fish, such as gouramis or medium-sized barbs, make excellent tankmates. Ropefish are remarkably fond of their own kind, and while they do not school as such, they are clearly most happy when kept in groups: three or four of ropefish will happily live together inside a cave or hollow ornament without any signs of aggression or territoriality. Bichirs, in contrast, tend to be rather snappy towards one another.
Ropefish are much more nocturnal than bichirs, and when first introduced tend to be extremely shy. Keeping them in groups will help them settle in more quickly, but equally important is providing plenty of shade. Floating plants are especially useful, particularly things like Ceratopteris and Ceratophyllum that are easy to grow and rapidly cover the surface of the tank, discouraging the fish from trying to escape. These fish are burrowers and appreciate a soft substrate, such as silica sand or peat, and this may restrict your options as far as rooted plants go; however, potted or sturdy species, like Echinodorus or Anubias, should work fine. As noted before, these fish like caves, so use plenty of stones and wood to create a complex environment within which these fish can feel secure.
Most likely you will find these fish being sold as juveniles around 30 cm in length, but adults can easily get to be two or three times as long. Obviously, these are quite sizeable fish and you will need to provide them with an appropriately large aquarium. They are quite slender though and not at all messy, so a 60 cm specimen is much less of a burden on the filter than, say, a 60 cm plec or cichlid.
The main problem with ropefish is likely to be feeding, since these fish do not show any interest in flake foods or things like catfish pellets. In the wild, these fish feed primarily on small animals including insect larvae, worms, shrimps, and of course small fish. Captive specimens happily accept bloodworms, mealworms, clam meat, and small strips of white fish. Water chemistry is of secondary importance, but one comment worth making is that while this fish can tolerate slightly brackish water, it does not need brackish water, and actually does best in soft, slightly acidic water.
As for their relatives, the bichirs, do they make good community fish? In some cases, yes, most notably Polypterus palmas and Polypterus senegalus, two relatively small species that may be territorial among their own kind but largely ignore other fish too big to eat. However, most of the other bichirs are large, aggressive, and often rather bad tempered fish best left in a species tank.
Freshwater butterflyfish, Pantodon bucholzi
The freshwater butterfly fish is a relative of the arowanas; both fish belong to the order Osteoglossiformes or ‘bony tongues’. As the name suggests, these fish have teeth on their tongues that help them grab their prey, principally small fish. The freshwater butterfly is a small animal though, typically reaching a length of around 10 cm in captivity, so while it is predacious towards things like guppies and danios, doesn’t post any kind of threat to fish of its own size, such as kribensis, climbing perch, and deep-bodied schooling fish like Congo tetras.
Apart from its predatory instincts, the freshwater butterfly is a relatively easy to keep oddball that can work well in a peaceful aquarium. It will eat a range of foods beyond small fish, including small insects such as crickets; mosquito and midge larvae, often referred to as ‘bloodworms’; and, once acclimated, flake. They ignore any food that sinks below the surface of the tank so don’t keep them with aggressive surface feeders likely to steal food from them before they get a chance to feed. Some peaceful bottom feeders, such as Corydoras, will clean up any food the freshwater butterflies miss.
From the normal perspective of the aquarist, looking at the fish from the side, freshwater butterflyfish are bizarre-looking animals with a mottled brown body and extremely elongated fin rays, especially those of the pelvic fins. So why are they called freshwater butterflyfish? Look at them from above and you’ll see that the pectoral fins are large, triangular, ornately pattered, and distinctly wing-like. I’d say they were a bit more like the wings of a moth than a butterfly, but that’s something you can decide for yourself.
These fish are very capable escape artists, and will leap out of the water if frightened, so it is essential that the aquarium is covered. Floating plants will help the fish settle in, but make sure that there is some open water so that they can feed properly. The only other issue to consider is water chemistry; like most other African blackwater fish, freshwater butterflyfish appreciate soft, slightly acidic water preferably filtered through peat.
Elephantnose fish, Gnathonemus petersi
Although among the most popular of all oddballs, the elephantnoses are large, rather territorial fish that present several challenges to the home aquarist. The prime problem with these fish is that they are very fussy eaters, and often need live foods when first introduced. When settled in, they usually take frozen bloodworms, mosquito larvae, and Tubifex worms as well, but while some specimens acquire a taste for things like catfish pellets later on, don’t rely on it. Since they are largely nocturnal, you will need to feed them at night. Because they can only swallow very small foods like worms and insect larvae, they don’t pose any threat to the other fish kept with them, so they can make good community tank residents. Among themselves, they tend to be territorial, the larger specimens bullying the smaller ones remorselessly. Consequently, unless you have a very large tank, only keep one specimen per tank.
Elephantnoses are members of a family of fish known as the Mormyridae that are widely distributed in Africa. Of the several mormyrids sold as aquarium fish, the elephantnose, Gnathonemus petersi, is by far the most widely traded. Among the other mormyrids, the only ones you are likely to see are the ‘baby whales’, Petrocephalus spp., and the ‘freshwater dolphins’, Mormyrus spp., and even these are relatively rarely seen animals. All mormyrids are capable of generating weak electrical fields that they use for navigation; they hunt using the senses of touch and taste, the trunk-like barbel on the chin of the elephantnose functioning in the same way as the whiskers of a catfish.
In the wild these fish inhabit murky water and are usually most active by night, therefore the aquarist will not see much of these fish if the aquarium is brightly illuminated. A thick growth of floating plants is probably essential, and as with the ropefishes discussed earlier, Ceratopteris and Ceratophyllum both make excellent choices being hardy and easy to grow. Elephantnoses are not fussy about water chemistry but slightly acidic or neutral water is probably best. Much more critical is getting the substrate right: these fish demand a soft substrate, ideally sand or peat but otherwise smooth, fine gravel will do. These fish spend most of their time rooting about the substrate, and sharp or coarse gravel will abrade the barbel and make the fish sensitive to bacterial infections that can eventually prove fatal. While these fish are not especially delicate, they do respond to copper-based medicines badly, so it is crucial to prevent diseases getting a foothold in your aquarium. Quarantining new stock, only buying from reputable retailers, and avoiding ‘dirty’ foods like live Tubifex all play a rôle in keeping elephantnoses (and other mormyrids) healthy.
Red-fin Distichodus, Distichodus affinis
Most fishkeepers associate characins with South America, but there are also many different kinds from Africa as well. Only a very few, most notably the Congo tetra, have become staples in the hobby, but there are lots of others well worth keeping. Among the African characins are Citharinidae, a small family including one genus, Distichodus, which includes a number or large, rather carp-like species that have acquired a modest degree of popularity. The six-striped distichodus, Distichodus sexfasciatus, for example is a jumbo-sized characin that makes a good companion for large catfish and peaceful cichlids. At the other end of the size spectrum is the dwarf distichodus, Distichodus decemmaculatus, which barely reaches 6 cm in length.
Lying between the two extremes is the red-fin distichodus, a handsome fish similar in size to a blue gourami and therefore an excellent proposition for the average home aquarium. It has a silvery-green body, bright red fins, and a distinctly rhomboid shape. Do note that juvenile red-fin distichodus are not strongly coloured, so tend to look rather drab in comparison (undoubtedly one reason they are often ignored by aquarists). Though not a schooling fish it is best kept in groups, it is completely harmless towards other fish and never engages in the fin-nipping behaviour that some other characins exhibit.
Like all the other Distichodus species, the red-fin distichodus is primarily vegetarian and will eat any soft green plants in the aquarium. Only things like foul-tasting species like Java fern and Java moss can survive in an aquarium containing these fish. On the other hand, if you’re among those aquarists that never have much success with plants, then this fish will justify your use of plastic plants! Given its vegetarian nature, a diet rich in greenstuffs is obviously important. Ideally, use a vegetarian flake food as a staple (such foods are commonly sold for livebearers and cichlids) and augment the diet with algae wafers, blanched lettuce, watercress, thin slices of courgette and cucumber, and crushed frozen peas. In other words, treat this fish as you would a small plec or a black molly.
Water chemistry is not particularly important, and neutral, soft to moderately hard water will do fine. Like most other characins, it appreciates a strong filter current and a high oxygen concentration, but otherwise places few demands on the aquarist. Because of its moderate size, hardiness, and peaceful nature it makes an excellent companion for many of the oddballs mentioned here. In particular, a group of these fish would work well with leopard bushfish, ropefish, and mormyrids as well other African species such as Congo tetras and Synodontis catfish.
Leopard bushfish, Ctenopoma acutirostre
Almost as a counterpoint to the characins, which we tend to think of as South American, the African examples of the labyrinth fish tend to be overshadowed by their Asian relatives, the bettas and gouramis. Nonetheless, the African labyrinth fish, commonly called climbing perches, are widespread and numerous, and several species are regularly traded as aquarium fish. Probably the most frequently seen is the leopard bushfish, a fairly small but highly predatory species appreciated for its lovely leopard-like colouration.
Few of the climbing perches are good all-rounders as far as life in the community tank goes, but the leopard bushfish comes close. It is hardy, completely peaceful, and easy to obtain. It is predatory though, meaning that the aquarist cannot keep it with very small companions. This fish will view neons, dwarf barbs, danios, and so on as food, but medium sized schooling fish such as Congo tetras, as will anything else too large to swallow whole, will be ignored. Leopard bushfish are notoriously shy, but become much more outgoing if kept with at least one or two other specimens of their own kind. On the other hand, overly active or aggressive species will cause them to hide; they do not work well with, for example, large cichlids or pufferfish.
The leopard bushfish is not nocturnal but it does like to lurk in shady places, and needs a tank with lots of plants (real or plastic), rocks, and bogwood. A thick layer of floating plants is useful, too. Like other labyrinth fish, leopard bushfish need to be able to breathe air, so make sure that the plants do not completely cover the surface of the tank.
As with most the fish mentioned here, water chemistry isn’t particularly important but neutral, soft to moderately hard water is the ideal. The main problem with keeping these fish is diet — they will not accept pellets or flakes. Frozen bloodworms and mosquito larvae are reliable alternatives to live fish, as are small invertebrates such as river shrimps and earthworms.
River goby, Dormitator lebretonis
Rounding off this selection of oddballs is a 10 cm long sleeper goby from West Africa known to inhabit both fresh and slightly brackish waters. Sometimes referred to as the ‘clay goby’ it isn’t an immediately impressive fish in the same way as, say, the Australian sleeper goby Morgunda morgunda; however, the river goby makes up for its more subdued colours by being peaceful and essentially non-predatory. It is also a comparatively small fish compared with some of the other sleeper gobies aquarists are likely to encounter, like the 30 cm spotted sleeper, Dormitator maculatus.
River gobies are omnivores and eat a wide range of foods including bloodworms, small pieces of prawn and white fish, and mysids; they also appreciate some green-stuffs in their diet, such as algae, vegetarian flake foods, and small pieces of boiled vegetables. While not a dedicated predator, the river goby will eat very small fish such as livebearer fry.
In terms of behaviour, these fish are midwater schooling fish, something that is rather uncommon for gobies. Groups of river gobies will hover or swim slowly in midwater picking off food that drifts by them; as such, they make excellent dither fish for benthic species such as dwarf cichlids that otherwise tend to be rather shy. Males are territorial but not to any great degree, and provided each fish has a cave or corner it can defend, serious problems will not occur.
Unlike the other fish discussed in this article, the river goby does not like soft or acidic water, and in fact requires moderately high pH and hardness levels similar to those that work well with fish like livebearers. Given the size and temperament of these fish, they can be an excellent choice for inclusion in a community containing swordtails, mollies, rainbowfish, and halfbeaks. River gobies also inhabit brackish waters and adapt well to low salinity systems containing fish such as kribensis, orange chromides, freshwater flatfish, and of course other gobies.
This selection of African freshwater fish barely scratches the surface as far as oddballs go; the advanced aquarist will find a wealth of more or less difficult species that merit this title in fishkeeping encyclopaedias and on web sites. A few, like the freshwater pipefish and the snakehead Channa obscura are demanding animals that are rarely traded and are best avoided by all but the most accomplished aquarists. Others, like the knifefish Xenomystus nigri and Playfair’s panchax are much easier to find and not at all difficult to keep. What they all demonstrate is that keeping African fish is about much more than just cichlids and catfish — there are plenty of options available to the ambitious aquarist looking to bring a bit of the Congo into their living room.