African Knifefish

Quick summary

The African Knifefish suits experienced aquarists who can provide a 250+ litre tank with plenty of hiding spots, dim lighting, and only tank mates too large to be eaten, since it is a nocturnal predator that can live over a decade. It is not ideal for beginners or community tanks with small fish, as it requires stable water quality, careful medication choices due to its scaleless body, and patience during feeding and acclimatisation.

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In this guide:

• Introduction
• Quick Stats
• Appearance
• Natural Habitat
• Tank Size and Setup
• Water Parameters
• Filtration and Equipment
• Diet and Feeding
• Behaviour and Temperament
• Tank Mates
• Breeding
• Common Diseases
• FAQs

Introduction

The African Knifefish (Xenomystus nigri) is a distinctive and fascinating freshwater species that has steadily gained a loyal following among experienced aquarists. Native to the rivers, lakes, and swamps of West and Central Africa, this nocturnal predator is admired for its elegant, blade-like body shape, its unusual swimming style, and its curious ability to produce audible sounds by expelling air from its swim bladder – a trait that can catch unsuspecting fishkeepers off guard the first time they hear it.

It is important to clarify a common point of confusion surrounding the name “knifefish.” The African Knifefish belongs to the family Notopteridae, commonly known as the Old World featherbacks or knifefishes. This family is entirely unrelated to the South American electric knifefishes of the order Gymnotiformes, which includes species such as the Banded Knifefish, Glass Knifefish, Brown Ghost Knifefish, and the Electric Eel. The term “knifefish” is simply a shared descriptive nickname applied independently to both groups because of their similarly compressed, blade-like body shapes and undulating anal fin locomotion. In reality, these two groups are separated by vast evolutionary distances, different continents, and fundamentally different biologies. Notably, the South American Gymnotiformes possess electroreceptive organs and, in some cases, powerful electric organs, whereas the African Knifefish and its Notopterid relatives have no such capability.

Within its own family, Xenomystus nigri is a genuinely unique fish. It is the sole member of the genus Xenomystus, and one of its most immediately recognisable features is the complete absence of a dorsal fin. This sets it apart from its larger and more commonly kept relative, the Clown Knifefish (Chitala ornata), and other members of the genus Chitala, all of which possess a small but clearly visible dorsal fin. The lack of a dorsal fin gives Xenomystus nigri an exceptionally smooth, unbroken dorsal profile, contributing to its streamlined, almost eel-like appearance as it glides through the water.

In the aquarium, the African Knifefish is a rewarding but somewhat demanding species. It is secretive and predominantly nocturnal, spending much of the daylight hours hidden among rocks, driftwood, or dense vegetation, and emerging at dusk to hunt. It requires a thoughtfully designed tank with ample hiding places, subdued lighting, and carefully chosen tank mates. While not aggressive in the typical sense, it is a predator that will readily consume any fish small enough to fit in its mouth. With proper care, this species can live for well over a decade, making it a long-term commitment for any aquarist who chooses to keep one.

Appearance

The African Knifefish has a highly distinctive body plan that immediately identifies it as a member of the knifefish group. The body is strongly laterally compressed – thin from side to side but deep from back to belly – giving it the characteristic blade or knife shape from which the common name derives. The body tapers smoothly towards the caudal region, and the overall silhouette is sleek and hydrodynamic, built for precise, controlled movement through densely vegetated or structurally complex habitats.

The most striking anatomical feature of Xenomystus nigri is its complete lack of a dorsal fin. While other Notopterid species, particularly those in the genus Chitala, retain a small dorsal fin, Xenomystus has lost this fin entirely. This gives the fish a smooth, uninterrupted dorsal outline from head to tail, contributing to its unmistakable appearance. The pectoral fins are well-developed and fan-shaped, used for delicate manoeuvring and hovering. The pelvic fins are either absent or vestigial, which is another distinguishing characteristic.

The primary means of locomotion is the enormously long anal fin, which extends from just behind the head along the entire ventral surface to the tip of the tail. This continuous, ribbon-like fin undulates in graceful, wave-like motions, allowing the fish to move forwards, backwards, and even hover in place with remarkable precision. This mode of swimming is mesmerising to watch and is one of the key attractions of keeping knifefish in general.

In terms of colouration, the African Knifefish is relatively understated compared to some of its more flamboyant tank mates. The base colour is typically a uniform dark brown to greyish-brown, sometimes with a slightly olive or purplish tinge depending on lighting conditions and the individual fish’s mood. Juveniles may display faint, irregular banding or mottling, but this usually fades as the fish matures, giving way to a more uniform adult colouration. The ventral surface tends to be slightly lighter. The eyes are proportionally large and well-adapted for low-light vision, reflecting this species’ nocturnal lifestyle.

The mouth is moderately sized, upturned, and capable of opening surprisingly wide relative to the fish’s head size. This is an adaptation for its predatory feeding habits, allowing it to engulf small fish and large invertebrates. The nostrils are tubular and prominent, extending slightly from the snout, which is thought to enhance the fish’s sense of smell – an important sensory tool for a species that hunts primarily in darkness.

Sexual dimorphism in the African Knifefish is subtle and difficult to determine with certainty outside of breeding condition. Mature females tend to be slightly fuller-bodied than males, particularly when gravid, but this difference is not always obvious. There are no reliable external colour or fin-shape differences between the sexes.

Natural Habitat

The African Knifefish is widely distributed across West and Central Africa, with its range encompassing river systems and associated floodplains in countries including Nigeria, Cameroon, the Democratic Republic of the Congo, the Republic of the Congo, Chad, Gabon, Sierra Leone, Liberia, and several others. It inhabits a variety of freshwater environments, but shows a clear preference for slow-moving or still waters with abundant cover.

In the wild, Xenomystus nigri is most commonly found in densely vegetated areas of rivers, streams, lakes, and seasonal swamps. It favours habitats with overhanging vegetation, submerged tree roots, fallen logs, and thick aquatic plant growth – anywhere that provides shelter from predators and strong currents during the daytime hours. These environments tend to have soft, slightly acidic to neutral water, often stained dark with tannins from decomposing leaf litter and organic matter. The substrates are typically sandy or muddy, with a thick layer of decaying plant material.

Water conditions in its native range are generally warm, soft, and slightly acidic, though the species has demonstrated considerable adaptability across a range of conditions given its extensive geographic distribution. Temperatures in these tropical freshwater environments typically range from 24 to 28 degrees Celsius year-round. The water is often low in dissolved minerals and may have very low visibility due to tannin staining and suspended particulate matter.

As a nocturnal species, the African Knifefish spends the daylight hours hidden among dense cover, becoming active at dusk and through the night. In the wild, its diet consists primarily of aquatic insects, insect larvae, small crustaceans, worms, and small fish. It is an opportunistic predator that relies heavily on its senses of smell and touch (via its sensitive body and fins) to locate prey in the dark.

The species’ ability to gulp air at the surface and produce audible sounds is particularly noteworthy. It can supplement its oxygen intake by swallowing atmospheric air, which is processed in a modified swim bladder. This adaptation allows it to survive in oxygen-poor waters, such as stagnant swamps and floodplain pools, where dissolved oxygen levels may drop to very low levels, particularly during the dry season. The audible croaking or grunting sounds it produces by expelling air from the swim bladder are thought to play a role in communication, particularly during social interactions or when the fish is stressed.

Tank Size and Setup

The African Knifefish requires a reasonably spacious aquarium to thrive. A minimum tank size of 250 litres is recommended for a single adult specimen. If you plan to keep more than one, or to house them alongside other medium-sized fish, a tank of 350 litres or more is advisable. Length is more important than height; a tank with a footprint of at least 120 cm in length provides adequate swimming space and territorial room.

The aquascape should be designed with the species’ nocturnal and secretive nature firmly in mind. Providing numerous hiding places is absolutely essential. This can be achieved through a combination of driftwood, bogwood, rock caves, PVC pipe sections, terracotta pots, and dense plantings. The fish needs to feel secure in one or more retreats during the day; without adequate hiding spots, it will be perpetually stressed, may refuse food, and will be vulnerable to disease.

Live plants are an excellent addition to an African Knifefish tank, both for their aesthetic value and for the additional cover they provide. Hardy, low-light species such as Java Fern (Microsorum pteropus), Anubias species, and Vallisneria are good choices, as they tolerate the subdued lighting that suits this species and are unlikely to be damaged by the fish’s movements. Floating plants such as Amazon Frogbit or Water Lettuce are particularly beneficial, as they reduce light penetration and create a more natural, shaded environment at the surface.

The substrate should ideally be soft and fine, such as sand or smooth, rounded gravel. The African Knifefish spends considerable time near the bottom of the tank and may rest on the substrate; sharp or coarse materials can damage its delicate ventral fin.

Lighting should be kept dim or moderate. Bright overhead lights will cause the fish to remain permanently hidden and can increase stress levels. If brighter lighting is needed for plant growth, use floating plants to create shaded areas, or employ a moonlight or blue LED setting during the evening to allow you to observe the fish during its active hours without disturbing it.

A tight-fitting lid is essential. While the African Knifefish is not an habitual jumper in the way that some species are, it is capable of leaping, particularly if startled or during initial acclimatisation to a new tank. The air space between the water surface and the lid should be maintained, as the species does gulp air periodically, and access to the surface must not be obstructed.

Water Parameters

The African Knifefish is reasonably adaptable when it comes to water chemistry, but it does best in conditions that approximate its natural habitat. Soft to moderately hard, slightly acidic to neutral water is ideal. Consistency and stability of parameters are more important than hitting an exact number; sudden swings in temperature, pH, or hardness are far more harmful than values that sit slightly outside the optimal range.

Regular water changes are important for maintaining water quality. A weekly water change of 25-30% is recommended, using dechlorinated water matched to the tank’s temperature. The African Knifefish is sensitive to poor water quality, particularly elevated levels of ammonia, nitrite, and nitrate. As a scaleless fish (it possesses very small, embedded scales that offer minimal protection), it is also more susceptible to dissolved medications and chemicals in the water, so care must be taken when treating the tank.

The addition of tannins, through the use of Indian Almond leaves, alder cones, or peat filtration, can be beneficial. Tannins soften the water slightly, lower pH gently, and create the dark, tea-stained conditions that closely replicate the species’ natural environment. Many keepers report that their African Knifefish are noticeably more confident and active in tannin-rich water.

Filtration and Equipment

Effective filtration is critical for keeping the African Knifefish healthy. As a messy eater that produces a fair amount of waste relative to its size, this species requires a filter capable of handling a significant biological load. A canister filter rated for at least 1.5 times the tank volume is a good starting point. Canister filters have the added advantage of producing a relatively gentle, diffused flow, which is preferable for this species.

The African Knifefish does not appreciate strong water currents. In the wild, it inhabits slow-moving or still waters, and excessive flow in the aquarium will cause stress. If your filter produces a powerful output, use a spray bar, lily pipe, or baffle to distribute and soften the flow. Position the outlet so that there are areas of near-still water within the tank where the fish can rest comfortably.

Biological filtration should be prioritised. Ensure your filter media includes plenty of high-surface-area biological media, such as ceramic rings, bio-balls, or sintered glass. Mechanical filtration through sponges and filter floss will help maintain water clarity and catch particulate waste. Chemical filtration with activated carbon can be useful for removing dissolved organic compounds, though it should be removed during any medication treatments.

A reliable heater with an accurate thermostat is essential, as this is a tropical species that requires stable, warm temperatures. An inline heater (connected to a canister filter) or a quality submersible heater with a guard is recommended. The guard protects the fish from burns, as the African Knifefish may rest against objects in the tank, including heaters, during the day.

An air pump is not strictly necessary, as the species can supplement its oxygen intake by gulping air at the surface. However, gentle surface agitation from the filter output is beneficial for overall gas exchange and oxygenation of the water column. Avoid overly vigorous aeration, which can create uncomfortable currents.

Lighting, as discussed above, should be subdued. A programmable LED light with adjustable intensity and a moonlight or twilight setting is ideal, as it allows you to observe the fish during its active hours without exposing it to harsh, bright conditions. A timer set to provide a natural day-night cycle of approximately 10-12 hours of light and 12-14 hours of darkness is recommended.

Diet and Feeding

The African Knifefish is a carnivore and a natural predator. In the wild, its diet consists of aquatic insects, insect larvae, small crustaceans, worms, and small fish. In captivity, it can be somewhat challenging to feed initially, particularly wild-caught specimens, which may refuse non-live foods for an extended period. However, with patience and persistence, most individuals can be weaned onto a varied diet of frozen and prepared foods.

The best staple foods for the African Knifefish include frozen bloodworms, frozen brine shrimp, frozen mysis shrimp, and frozen krill. Chopped earthworms and white worms are also readily accepted and provide excellent nutrition. Live foods, such as blackworms, tubifex worms (from a clean source), and live brine shrimp, are highly appreciated and can be used to entice reluctant feeders or to condition fish for breeding.

Some specimens can be trained to accept high-quality sinking carnivore pellets or wafers. This is beneficial for long-term convenience and nutritional consistency, but should not be relied upon as the sole food source. The transition to prepared foods should be done gradually, often by mixing pellets with frozen or live foods until the fish begins to accept them independently.

Feeding should primarily take place in the evening or after lights-out, corresponding to the species’ natural nocturnal activity pattern. Many keepers find that their African Knifefish will barely feed during daylight hours but becomes an enthusiastic and voracious eater once the tank is dark. Offering food near the fish’s favourite hiding spot can help ensure it gets enough to eat, particularly in a community tank where diurnal species may consume food before the knifefish emerges.

Feed once or twice daily, offering an amount the fish can consume within a few minutes. Avoid overfeeding, as uneaten food will quickly foul the water. Juvenile fish benefit from more frequent feeding – two to three small meals per day – to support their growth. Adult fish can be fed once daily, with an occasional fast day each week to maintain good digestive health.

Feeder fish should be avoided as a regular food source. They carry a high risk of introducing parasites and diseases, and they do not provide a balanced nutritional profile. If live fish are offered, they should be home-bred and quarantined to minimise disease risk.

Behaviour and Temperament

The African Knifefish is a predominantly nocturnal, secretive, and solitary species. During the day, it will typically be found tucked away in its preferred hiding spot – wedged between rocks, concealed inside a cave, or resting among dense plant growth. It can remain remarkably still for hours, with only the gentle undulation of its anal fin betraying the fact that it is alive and aware.

As dusk approaches and the tank lights dim or switch off, the fish undergoes a marked transformation. It emerges from its hiding place and begins actively patrolling the tank, investigating its surroundings, and hunting for food. Its movement is graceful and mesmerising; the long anal fin ripples continuously, propelling it forwards, backwards, and even vertically with equal ease. It can hover in place and change direction instantly, demonstrating a level of manoeuvrability that few other aquarium fish can match.

One of the most remarkable behaviours of the African Knifefish is its ability to produce audible sounds. By expelling air from its swim bladder, it generates a croaking, grunting, or clicking noise that can be clearly heard from outside the tank. This behaviour is most commonly observed during feeding, when the fish is startled, or during social interactions with conspecifics. While the exact purpose of these vocalisations is not fully understood, they are thought to play a role in communication, territorial signalling, and possibly courtship.

Regarding conspecifics, the African Knifefish can be kept singly or in small groups, but the latter requires careful consideration. Individuals can be territorial and aggressive towards one another, particularly in tanks that lack sufficient hiding places or space. In a sufficiently large tank (350 litres or more) with multiple hiding spots and broken sightlines, a small group can coexist, though some chasing and minor squabbling is to be expected. In smaller tanks, keeping a single specimen is usually the safest approach.

Towards other species, the African Knifefish is generally peaceful, provided its tank mates are too large to be swallowed. It is not a fin-nipper or a bully in the conventional sense, but it is an opportunistic predator. Any fish small enough to fit in its mouth will be eaten, typically under cover of darkness. This means that small tetras, guppies, endlers, and similarly diminutive species are not suitable companions.

The African Knifefish can be somewhat shy and easily stressed, particularly during the initial period after introduction to a new tank. Sudden loud noises, vibrations, and rapid movements near the tank can cause it to panic and dart erratically, sometimes injuring itself against the glass or decor. A calm, quiet location for the tank and a gradual acclimatisation process are important for helping the fish settle in.

Tank Mates

Choosing appropriate tank mates for the African Knifefish requires balancing several factors: the knifefish’s predatory nature, its nocturnal habits, its preference for calm conditions, and its sensitivity to aggression from boisterous or territorial species. The ideal tank mate is a peaceful to moderately active fish that is too large to be eaten, does not compete aggressively for hiding spaces, and does not harass or nip at the knifefish’s long, vulnerable anal fin. Avoid very small fish, highly aggressive cichlids, and any species that may out-compete the knifefish for food during nocturnal feeding.

Good tank mates

• Congo Tetra – A peaceful, appropriately sized African tetra that shares similar water parameter preferences and is too large to be eaten by most adult knifefish.
• Synodontis eupterus – A hardy, peaceful African catfish that occupies the bottom of the tank and is unlikely to conflict with the knifefish.
• Bristlenose Pleco – A peaceful algae-eating catfish that stays out of the knifefish’s way and adds useful clean-up duties to the tank.
• Angelfish – A calm, slow-moving cichlid that is generally too large and tall-bodied to be eaten, and tends to occupy midwater levels.
• Pearl Gourami – A peaceful, appropriately sized labyrinth fish that prefers similar water conditions and does not exhibit aggressive tendencies.
• Rainbowfish – Active but peaceful schooling fish that are generally too large for the knifefish to prey upon and add colour to the upper water column.
• Leopard Bush Fish – A fellow African species with similar nocturnal habits and water parameter preferences; both species tend to ignore each other provided there is sufficient space.
• Kribensis – A small but robust West African cichlid that is generally fast enough and too deep-bodied to be eaten by an adult knifefish.

Fish to avoid

• Neon Tetra – Far too small and will be consumed by the knifefish during nocturnal hunting.
• Guppy – Small, slow, and an easy target for any predatory fish; these will be eaten quickly.
• Tiger Barb – A known fin-nipper that is likely to harass the knifefish and damage its long anal fin.
• Oscar – A large, aggressive cichlid that will bully or potentially injure the knifefish, and requires different tank conditions.
• Red Devil Cichlid – Highly aggressive and territorial; will attack and likely kill the knifefish.
• Cherry Shrimp – Small invertebrates are a natural food source for the knifefish and will be eaten immediately.
• Endler’s Livebearer – Far too small to be kept with any predatory fish; will be treated as food.

Breeding

Breeding the African Knifefish in captivity is a challenging endeavour that has been achieved only sporadically by dedicated aquarists. The species is not commonly bred in home aquaria, and much of the stock available in the trade is wild-caught. However, successful breeding has been documented, and understanding the process is valuable for anyone who wishes to attempt it.

The first challenge is sexing the fish, as external differences between males and females are minimal. Females in breeding condition tend to be noticeably plumper than males when viewed from above, but this is not a reliable indicator outside of the breeding season. Obtaining a group of six or more juveniles and allowing them to grow and pair off naturally is considered the most effective approach.

To trigger spawning, conditions should mimic the onset of the rainy season in the species’ native habitat. This can be simulated by performing a series of large, slightly cooler water changes (dropping the temperature by one to two degrees Celsius), increasing water flow slightly, and adjusting the photoperiod. Soft, acidic water (pH 6.0-6.5, GH 3-6 dGH) and a diet rich in live and frozen foods are also important conditioning factors.

The African Knifefish is a substrate spawner. The female deposits a relatively large number of adhesive eggs – sometimes several hundred – on a flat surface such as a smooth rock, a piece of slate, or a broad plant leaf. Reports vary regarding parental care; in some cases, the male has been observed guarding the eggs, while in others, both parents appear to participate in brood defence. However, parental care in captivity is not always consistent, and some pairs may consume their own eggs if disturbed or stressed.

Eggs typically hatch within three to five days at temperatures around 26-28 degrees Celsius. The fry are small and initially subsist on their yolk sacs before transitioning to tiny live foods such as infusoria, freshly hatched brine shrimp nauplii, and microworms. Growth is relatively slow, and the fry require meticulous water quality management and frequent small feeds throughout the day.

Raising the fry is arguably the most challenging part of the process. They are delicate, sensitive to water quality fluctuations, and vulnerable to fungal infections. A dedicated rearing tank with gentle sponge filtration, stable temperatures, and minimal disturbance is essential. Regular small water changes – daily if possible – help maintain the pristine conditions the fry need to survive and develop.

Common Diseases

The African Knifefish is susceptible to the same range of freshwater diseases as most tropical fish, but its physiology makes it somewhat more vulnerable to certain conditions and more sensitive to common treatments. The fact that it possesses only very small, deeply embedded scales means that its skin offers less protection against parasites and pathogens, and it is more prone to absorbing chemicals – including medications – directly through its skin.

White spot disease (Ichthyophthirius multifiliis, or Ich) is one of the most common ailments encountered. It presents as small white cysts on the body and fins and is typically triggered by stress, temperature fluctuations, or the introduction of new, unquarantined fish. Treatment with standard Ich medications should be approached with caution; the African Knifefish is sensitive to many common treatments, particularly those containing copper or malachite green. Half-dose treatments, combined with raising the temperature to 30 degrees Celsius and adding aquarium salt at a low concentration (1 gram per litre), are often a safer first line of defence. Always research the specific medication’s compatibility with scaleless fish before use.

Bacterial infections, including fin rot and skin ulcers, can occur, particularly in tanks with poor water quality or when the fish has sustained physical injuries (from sharp decor, aggressive tank mates, or collision with the glass during panic). Maintaining excellent water quality is the single most important preventative measure. Mild cases often resolve with improved water conditions alone; more serious infections may require treatment with antibacterial medications safe for scaleless fish.

Fungal infections, presenting as white, cotton-like growths on the body or fins, are another risk, especially following physical injury or in tanks with high levels of organic waste. Good hygiene, prompt removal of uneaten food, and regular water changes are the best preventative strategies.

Internal parasites can be a concern, particularly in wild-caught specimens. Signs include weight loss despite a good appetite, white or stringy faeces, and lethargy. A course of anti-parasitic treatment formulated for sensitive species may be necessary. Quarantining all new fish for a minimum of two to four weeks before adding them to the main tank is strongly recommended.

Stress-related issues are perhaps the most insidious threat to the African Knifefish’s health. Chronic stress caused by inadequate hiding places, overly bright lighting, aggressive tank mates, or poor water quality weakens the immune system and makes the fish susceptible to a wide range of secondary infections. Addressing the root cause of stress is always more effective than treating the symptoms.

FAQs

Can I keep the African Knifefish in a community tank?

Yes, the African Knifefish can be kept in a community tank, but only with appropriately chosen tank mates. All companions must be too large to be swallowed – a good rule of thumb is that no fish should be less than half the length of the knifefish’s head width. Avoid aggressive species that may bully the knifefish, and avoid fin-nippers that may damage its long anal fin. Peaceful, medium-sized species from similar habitats are the best choices.

Why does my African Knifefish make strange noises?

The African Knifefish is one of a relatively small number of aquarium fish that can produce audible sounds. It does this by expelling air from its swim bladder, creating a croaking, grunting, or clicking noise. This behaviour is perfectly normal and is thought to serve a communicative function, particularly during social interactions, feeding, or when the fish is startled. It is not a sign of distress in itself, though frequent vocalisation in a newly introduced fish may indicate it is still adjusting to its environment.

Is the African Knifefish related to the Black Ghost Knifefish?

No, despite sharing the common name “knifefish,” the African Knifefish (Xenomystus nigri) and the Black Ghost Knifefish (Apteronotus albifrons) are not closely related. The African Knifefish belongs to the family Notopteridae (Old World featherbacks), while the Black Ghost Knifefish belongs to the order Gymnotiformes (South American electric knifefishes). The name “knifefish” is a descriptive term applied independently to both groups because of their similar body shapes, but they are separated by vast evolutionary distances and are found on different continents.

How long does it take for an African Knifefish to settle into a new tank?

The African Knifefish can

Related Guides

• False Tiger Knifefish – Tank Setup, Feeding and Breeding – A fellow member of the knifefish group with similar body shape, nocturnal habits, and care requirements, making it a natural comparison for anyone interested in keeping knifefishes.
• Demon Eartheater – Tank Setup, Feeding and Breeding – A sizeable, peaceful South American cichlid that thrives in similar water parameters and can make a suitable tank mate for larger predatory species like the African Knifefish.
• Altum Angelfish – Tank Setup, Feeding and Breeding – Another large, deep-bodied species requiring spacious tanks and stable soft-water conditions, offering useful parallels in advanced freshwater husbandry.
• Dwarf Pleco – Tank Setup, Feeding and Breeding – A nocturnal, bottom-dwelling species that shares the African Knifefish’s preference for dim lighting and plenty of hiding places, and can coexist peacefully in a well-designed setup.
• L168 Butterfly Pleco – Tank Setup, Feeding and Breeding – Another shy, cave-dwelling species suited to low-light aquariums, providing insight into creating the kind of shelter-rich environment that benefits the African Knifefish.