Tetraodon Mbu Care Sheet

Macauley Sykes
Jan 22, 2022
25 min read

Updated: Sep 11

This care sheet is written with the aim of providing optimal care for this species of fish.

Pufferfish Enthusiasts Worldwide endeavours to inspire and promote the highest standards of care - not basic or minimum care - using the best evidence available at the time.

Introduction

The Mbu Puffer (Tetraodon mbu) is the undisputed giant of the freshwater pufferfish world. It is native to Central Africa, with a distribution spanning much of the Congo River Basin, including the wide expanse of Pool Malebo (Kinshasa–Brazzaville) and extending into Lake Tanganyika. Within this range, it inhabits a variety of habitats, from the main river channels to floodplain margins and lacustrine waters.

First described in 1899 by George Boulenger, this species is instantly recognisable by its bold reticulated pattern, massive size, and commanding presence. Among aquarists, it is admired not only for its beauty and intelligence but also for the sheer challenge of providing for such a demanding fish.

Adults commonly reach 50–60 cm (20–24″), with verified records up to 67 cm (26″), placing them far beyond the scope of conventional aquaria. The verified maximum size is 67 cm Total Length (TL), recorded in field studies and reference databases such as FishBase. Anecdotal reports from aquarists and collectors suggest that exceptional specimens may reach up to 76 cm TL, though these claims exceed the documented record.

For clarity, all sizes reported here are given as Total Length (TL), measured from the tip of the snout to the end of the caudal fin.

What sets the Mbu apart from many other puffers is not just its bulk, but its behaviour. Despite their formidable jaws and predatory instincts, Mbu puffers are often described as highly observant, intelligent, and interactive, developing strong associations with their keepers.

With proper care in enormous, specialised enclosures, Mbu puffers can thrive for over two decades, offering one of the most charismatic and rewarding fishkeeping experiences available. Their vast size, combined with a potential lifespan of 15–20 years or more in captivity, makes them one of the most significant long-term commitments in freshwater fishkeeping.

In the wild

The Mbu Puffer (Tetraodon mbu) is widely distributed across the Congo Basin of Central Africa, with confirmed records from Pool Malebo at Kinshasa–Brazzaville, the mainstem Congo River both upstream and downstream, and lacustrine habitats such as Lake Tanganyika.

This broad range makes it one of the most adaptable African puffers, able to thrive in both soft, acidic river water and the alkaline, mineral-rich conditions of the Great Lakes.

Pool Malebo is a natural focal point for the species. This vast expansion of the lower Congo is ~35 km long and 23–25 km wide, with depths usually between 3 and 10 m depending on the season. At its centre lies Mbamu Island, which divides the flow and creates a mix of open channels, sandbanks, and sheltered littoral habitats. Seasonal floods expand the shoreline by several kilometres, flooding forest and grassland, and introducing large pulses of organic matter and invertebrates into the system.

Hydrological surveys around Kinshasa–Brazzaville describe Pool Malebo as a warm, soft-water environment with very low mineral content.

Measured parameters include:

Temperature: ~26–28 °C (mean 27.7 °C ± 1.6)
pH: 6.0–6.7 (slightly acidic, seasonal variation)
Conductivity: 28–37 µS cm⁻¹ (extremely soft water)

In stark contrast, Lake Tanganyika presents a very different chemical profile:

Temperature: ~24–28 °C at the surface
pH: 8.4–9.2 at the surface (gradually lower with depth)
Conductivity: ~670–700 µS cm⁻¹ in the upper 0–100 m

The T. mbu occurs in both systems and demonstrates extraordinary ecological flexibility. In the Congo, it inhabits soft, slightly acidic, dynamic waters, while in Tanganyika, it lives in some of the hardest, most alkaline freshwater in the world.

Ecologically, the Mbu is an active forager of open channels, floodplain margins, and lake shallows. Its fused dental plates are adapted to a durophagous diet dominated by molluscs and crustaceans. Freshwater snails such as Biomphalaria spp. and Melanoides tuberculata, along with unionid clams, provide abundant calcium-rich prey. Crustaceans also feature heavily, including shrimp (Caridina spp.) and several freshwater crabs native to its range, among them Potamonautes congoensis, P. langi, P. stanleyensis, Acanthothelphusa lirrangensis, and Arcopotamonautes platynotus in Lake Tanganyika.

These hard-shelled prey are essential in wearing down the fish’s continuously growing beak. Opportunistic feeding is also likely, with juveniles and adults taking insect larvae, worms, and occasionally small fish when encountered.

Predation pressure on adult Mbu puffers is generally low due to their size, dentition, and the presence of tetrodotoxin or related toxins. However, they are not invulnerable: clawless otters (Aonyx spp.) have been filmed by National Geographic attacking Mbu puffers in the Congo, demonstrating that specialised mammalian predators are capable of exploiting them. Juveniles are at greater risk, being vulnerable to large fish, aquatic birds, and crocodilians, and rely on camouflage and inflation to survive.

For aquarists, this wild context is highly instructive. It explains the species’ need for immense swimming space, consistently high oxygenation, and pristine water quality. It also highlights the importance of a complex, varied diet that reflects the diversity of prey found in its natural range. Without regular access to suitably hard-shelled foods to wear down the beak, Mbu puffers are prone to dental overgrowth and associated health problems. Understanding the life of Tetraodon mbu in the Congo and Tanganyika systems reveals both the reasons behind its remarkable adaptability and the immense challenge of providing for it in captivity.

Conservation & Trade

The conservation status of the Mbu Puffer (Tetraodon mbu) is currently not assessed by the IUCN Red List, and there are no population-level studies that quantify its abundance across the Congo Basin. Its broad distribution, spanning both the Congo River system and Lake Tanganyika, suggests a more resilient status than narrowly restricted species such as T. schoutedeni. Nevertheless, the absence of ecological monitoring means that its long-term outlook remains uncertain.

Environmental Pressures

Like all species in the Congo Basin, T. mbu is exposed to multiple anthropogenic pressures, especially in regions near dense human populations such as Kinshasa and Brazzaville.

These include:

Water pollution from sewage, industrial effluents, and urban runoff entering the Congo River.
Habitat degradation from deforestation, mining activity, and agricultural expansion along river margins and floodplains.
Overfishing and bycatch, where artisanal nets and traps intended for food fishes may capture puffers incidentally.
Introduced species and aquatic weeds, such as water hyacinth (Eichhornia crassipes), which form dense mats that reduce oxygen levels and disrupt littoral habitats.

Although the Mbu is highly adaptable, occurring in both the soft, slightly acidic waters of the Congo and the hard, alkaline conditions of Tanganyika, its reliance on abundant molluscan and crustacean prey means that degradation of benthic invertebrate populations could have cascading effects on its ecology.

Sustainability Outlook

Unlike some ornamental fishes, the Mbu puffer is not harvested in large numbers. Its extreme size, rapid growth, and demanding care requirements make it a niche species in the aquarium trade, primarily exported as juveniles. There is no evidence of significant over-collection at present, though all individuals available to aquarists are wild-caught; captive breeding has never been documented.

For now, the greater risks to T. mbu lie not in trade but in the long-term environmental health of the Congo Basin. Ongoing urban expansion, pollution, and unsustainable resource use around Pool Malebo and other parts of the basin continue to degrade water quality and habitat complexity. While the species’ wide distribution may buffer it against immediate threat, the lack of monitoring means future declines could go unnoticed.

In the aquarium

The Mbu Puffer is a species that combines large size with high intelligence, and these two traits dictate almost every aspect of its captive care. An aquarium for Tetraodon mbu must be built on a very different scale from that of most home aquariums. This is not a species to be “grown out” and later rehomed: the commitment must be there from the very first day. Only aquarists with the space, resources, and long-term vision to provide a system measured in the thousands of litres should attempt to keep one.

Even with careful planning, aquarists quickly discover the extraordinary challenges of housing an adult Mbu. Within Pufferfish Enthusiasts Worldwide, members have shared stories of aquaria that had to be built inside their homes because they could not fit through doors, of floors reinforced with steel beams to bear the weight of multi-tonne tanks, and of steel stands welded in situ to support custom glasswork.

The expenses often extend well beyond the aquarium itself, encompassing electrical upgrades, water-management systems, and even structural renovations. These real-world experiences underline why Tetraodon mbu is a species that few can realistically commit to keeping.

The layout of such a system is as important as its size. In the wild, Mbu are not fish of barren open water but of complex riverscapes, floodplains, and lake margins. They are active cruisers that need long, open swim lanes, yet they also require harbourage: caves, overhangs, shaded areas, and other structures that provide security.

A well-designed aquarium strikes this balance, giving the fish the confidence to explore while offering quick refuge whenever it feels threatened.

Enrichment is central to their welfare. Mbu puffers are curious, intelligent, and often destructive when bored. Without stimulation, they may tear up plants, move décor, or even attempt to dismantle equipment inside the tank. Environmental complexity (varied flow, structured décor, and feeding methods that encourage foraging) is therefore not optional but essential. Interaction with the aquarist also plays a key role, helping direct this energy into positive behaviours.

Scaping for scale means thinking well beyond ordinary aquarium décor. Keepers will inevitably find themselves looking towards the XXL scaping sections of their local fish stores. Large, stable boulders, hefty root-like wood, and architectural rockwork are all appropriate choices.

Two main approaches work well:

Rocky, lake-like layouts, inspired by Lake Tanganyika, use substantial rock formations to create overhangs and shaded retreats while maintaining broad open corridors.
River-delta biotopes, echoing the Congo floodplains, combine driftwood, roots, and rounded stonework to form cover and structure.

In both cases, the scape must balance ample swimming space with secure harbourage. All décor must be stable and free of sharp edges, as an Mbu is capable of knocking down or shifting anything not firmly fixed.

Plants are best treated as optional enrichments. Many species will be uprooted or shredded, but tough epiphytes such as Anubias and Microsorum (Java fern) can sometimes be established on large wood or rock. Crinum natans has also been kept successfully in well-protected corners. Floating cover like Ceratopteris or Pistia can help create shade. Any attempt at planting must be realistic: the Mbu may eventually destroy them, and the scape should never rely on plants as its foundation.

Filtration and oxygenation must also be up for the job. Mbu puffers produce heavy waste loads and are intolerant of declining water quality, especially elevated nitrate. Some keepers use high-capacity canister filters such as the Fluval FX6 or Eheim Pro3+ 1200XL, and while these can handle large volumes of water, the sheer scale of an adult Mbu system makes sump filtration the superior choice. A sump not only adds water volume and promotes gas exchange, but also keeps vulnerable equipment (such as heaters) out of reach.

This precaution is essential because Mbu puffers are more than capable of biting through heater casings, filter guards, and even power cables. All in-tank equipment must be bite-proof, and every cable must be routed externally or shielded in rigid (preferably stainless steel) conduit. Wavemakers and pumps must always be fitted with guards to prevent injury and damage.

With the correct balance of swimming space, harbourage, enrichment, robust scaping, and uncompromising water quality, an Mbu puffer can live for well over 20 years. Few freshwater fish offer such charisma, but equally few demand such commitment. Keeping Tetraodon mbu successfully means making space in your home, and in your life, for a fish that might be with you for decades.

Substrate

The Mbu Puffer is a wallowing species, especially in its juvenile stages. In the wild, young fish regularly bury themselves in soft sediment, and aquarists should always provide them with the opportunity to express this behaviour in captivity.

For a species that spends much of its time resting or patrolling open water, wallowing is both a comfort and an instinctive survival strategy.

You can read more on suitable substrates here: What is the best substrate for wallowing pufferfish?

Why do Mbu puffers wallow?

Wallowing serves several purposes:

Ambush: burying to surprise prey, lying in wait with only the eyes exposed.
Camouflage: concealing themselves from larger predators.
Rest: settling securely beneath the substrate, where they feel protected and hidden.

For juveniles and sub-adults, wallowing is common. However, it is important to note that fully grown Mbu puffers do not always engage in wallowing, and some adults rarely or never exhibit the behaviour. Even so, the provision of a safe, suitable substrate is strongly recommended, as it preserves the option for natural behaviour and provides enrichment should the fish choose to use it.

Choosing the right substrate

Because Mbu puffers dive head-first into the substrate and then push forward with their tails, the texture of the material is critical. A coarse or sharp substrate will cause scrapes and abrasions, leaving the fish vulnerable to bacterial or fungal infections.

Ideal choice: fine, sugar-soft sand.

Grain size: 0.2–0.5 mm (very fine, smooth sands).
Best types: aquarium-grade fine sands, well-rinsed play sand, or smooth pool filter sand that is chemically inert and free from sharp grains.
Avoid: gravel, plant soils, or coarse sands. Even rounded gravels prevent proper wallowing and may injure the fish when it attempts to bury.

Depth and maintenance

The depth of sand should always match the depth of the fish’s body, allowing full burial if desired. For young Mbu, a shallow bed is adequate, but as the fish grows the substrate should be gradually deepened.

Sand can trap waste and compact over time, creating anaerobic pockets where harmful gases accumulate. The Mbu will stir the sand naturally through its own movements, but this is not enough in deeper beds.

Aquarists should:

Keep the sand bed 2–5 cm deep in most areas, adding more only where the fish frequently wallows.
Stir or rake sections during weekly water changes to release trapped gas and circulate oxygen.
Use good flow to keep the surface layers moving and prevent detritus from settling.
Vacuum lightly over the surface when siphoning, rather than deeply disturbing the bed each time.

Substrate colour

Like other puffers, Mbu can adjust their colouration to match their environment. A paler sand substrate often brings out their most striking reticulated patterns, while darker sands may cause them to appear more subdued. For most aquarists, pale or natural-toned sand is the most visually rewarding option.

Bare-bottomed / Tile-bottomed Tanks

Some aquarists may be tempted to run bare-bottomed or tile-bottomed aquaria for an Mbu puffer, often believing that they are easier to keep clean or that they create a sharper, more modern aesthetic. While this approach may suit certain species, it is not appropriate for a natural wallower like the Mbu.

Bare-bottomed tanks deny the fish the chance to express a key natural behaviour.

Wallowing is more than just “something they sometimes do”: it is a fundamental part of their behavioural repertoire, particularly in juveniles and sub-adults. Removing substrate for the sake of convenience is effectively depriving the animal of essential enrichment.

A Mbu puffer is at its healthiest and happiest when provided with a safe, fine sand substrate that allows it to bury if it chooses. Even if a fully grown adult rarely wallows, the option should still be available. The long-term welfare of the fish must always take precedence over the keeper’s preference for ease of maintenance or a minimalist display.

At Pufferfish Enthusiasts Worldwide, we consistently encourage naturalistic aquaria that prioritise the needs of the fish and replicate, as closely as possible, the environments these species evolved in. A Mbu puffer should always be allowed to interact with its substrate and environment in ways that come naturally to it.

The only circumstances in which a bare-bottomed setup may be justified are short-term situations such as quarantine or during anti-parasitic worming treatment, where ease of cleaning and observation are critical. Outside of these controlled cases, a bare-bottomed or tile-bottomed tank has no place in the long-term housing of Tetraodon mbu.

Tank size

An adult Mbu puffer is an extraordinary fish to house, both in scale and in behaviour. Reaching up to 67 cm (26″) in total length, and with a heavy, muscular build, this species is not only large but also active, inquisitive, and constantly on the move. Any aquarium designed for it must therefore prioritise length for cruising, depth for turning, and structural stability to support tonnes of water and décor.

The absolute lower limit for a single specimen is 8 × 3 × 3 ft (around 2,000 litres / 540 US gallons). Even at this scale, space is only just sufficient: three feet of depth gives a full-grown Mbu just enough room to turn, while eight feet of length provides only a few body lengths of swimming distance. Larger systems are always preferable, not only for the fish’s welfare but also for ease of aquascaping and maintenance.

In practice, aquariums of this size are basically never available off the shelf. Most Mbu keepers commission custom-built tanks or indoor ponds tailored to their homes.

Within Pufferfish Enthusiasts Worldwide, members have reported aquaria constructed inside the house because they would not fit through doorways, floors reinforced with steel to carry the immense load, and welded stands built in place to bear the weight. These experiences highlight the reality of keeping this species: it is as much a structural project as it is an aquarium.

This level of planning and expense may sound daunting, but it is the only way to house an animal of this scale responsibly. Aquarists who commit to the challenge are rewarded with a charismatic, intelligent companion, but the decision must always begin with a sober understanding of the space and engineering required.

Falsehoods about the size of captive mbu puffers

One of the most common things you’ll hear about Mbu puffers is: “They don’t grow as big in captivity as they do in the wild, so you don’t really need a massive tank.”

It sounds plausible at first, after all, many of us have seen undersized puffers in small aquaria, but when you stop and think about it, the reasoning quickly falls apart. In fact, if anything, captive Mbu puffers should have a better chance of reaching their full size than wild ones.

In the wild, growth is limited by seasonal famines, parasite loads, pollution, predation, and competition for food.

In a well-managed aquarium, all of those pressures are removed:

Year-round nutrition replaces feast-and-famine cycles.
Parasites and disease can be eradicated or treated.
Stable, pollutant-free water removes environmental stress.
No predators, no competition means more energy for growth.
Low stress = higher efficiency: calmer fish absorb and use nutrients more effectively.

So why do so many people still believe captive Mbu stay small? For decades, puffers were kept in aquaria that were simply too small, fed poor diets, or left in substandard water quality. These conditions stunt growth, but that isn’t the fault of captivity itself; it’s the fault of poor/inadequate husbandry.

Once you see it this way, the myth unravels. It’s not that Mbu puffers can’t grow large in aquaria; it’s that too many have been denied the conditions they need. With proper care, a captive Mbu should not only reach its wild size but may even live longer than its river-dwelling relatives.

This is why recommendations for enormous aquaria are not exaggerations: they are based on what a healthy, well-kept Mbu really becomes.

Water values

Maintain the following water parameters:

Temperature: 25–27 °C (77–81 °F)
pH: 6.8–8.0
GH: 5–15 °dGH (avoid extremes; stability first)
Ammonia (NH₃): 0 ppm
Nitrite (NO₂⁻): 0 ppm
Nitrate (NO₃⁻): <10–15 ppm (the lower, the better)

Why these numbers?

The recommended parameters for Tetraodon mbu reflect both the chemistry of its natural habitats and the practical adjustments needed for long-term success in captivity.

In the Congo River at Pool Malebo, Mbu live in warm, soft, slightly acidic water (26–28 °C, pH 6.0–6.7, conductivity ~30 µS cm⁻¹). At the other extreme, Lake Tanganyika supports populations in consistently hard, alkaline conditions (24–28 °C, pH 8.9–9.4, conductivity ~620–700 µS cm⁻¹). This striking contrast shows how adaptable the species is across its range.

However, there is no evidence that individual fish migrate between the two systems. Given the separation of the Congo and Tanganyika basins, such large-scale movements seem unlikely, though they have not been formally ruled out. It is more reasonable to assume locally resident populations adapted to their respective chemistries.

For aquarists, this reinforces the value of a balanced middle ground in captivity: conditions that avoid the extremes of either habitat while remaining safe, stable, and manageable in large aquaria.

If provenance is known, it can be interesting to consider whether a specimen was collected from Congo or Tanganyika, as this may explain subtle differences in tolerance or behaviour. In practice, though, many imports arrive without collection data (or it's lost), so aquarists should plan for a generalist approach.

Our recommendations sit comfortably between the two wild extremes.

They provide mineral support, buffering, and long-term stability without straying into impractical territory.

Ammonia and nitrite must always be zero, as puffers are acutely intolerant of nitrogenous waste. The nitrate benchmark is less a toxicity cut-off than a proxy for overall cleanliness: chronic exposure to elevated nitrate is known to reduce growth, weaken immune function, and shorten lifespan in freshwater fishes.

By aiming for this sensible middle ground, aquarists create an environment that reflects the Mbu’s natural adaptability while ensuring long-term health in the closed system of an aquarium.

Tankmates

The Mbu puffer is sometimes described as a “peaceful giant,” but this description can be misleading.

In truth, Tetraodon mbu is a large but sensitive fish. It does not seek conflict and is rarely aggressive without cause, but it is highly susceptible to stress, and its enormous bite power means that even an accidental nip can be catastrophic for other fish.

In its native range, the Mbu shares water with some of Africa’s largest and most aggressive fishes, including the Emperor cichlid (Boulengerochromis microlepis), Goliath tigerfish (Hydrocynus goliath), and several large catfishes. Rather than confronting these species, Mbu survive by avoiding them. This deeply ingrained instinct to evade large, fast, or territorial fish does not vanish in captivity.

A puffer housed with such companions will often show signs of chronic stress: hugging the substrate, hiding frequently, or refusing to venture into open water. T

his is especially true when large fish dominate the upper levels of the tank. For a naturally cautious species like the Mbu, the constant presence of big, overhead swimmers is interpreted as a threat. Even without aggression, the result is a puffer that is anxious, reclusive, and unable to behave naturally.

Water chemistry matters

Another overlooked factor is water parameter compatibility. Mbu puffers thrive in a mid-range (pH 6.8–7.8, GH 5–15 °dGH), reflecting their adaptability across Congo and Tanganyikan waters. Compatibility must therefore be judged not only by temperament but also by shared environmental requirements.

Suitable companions

When tank mates are attempted, they should be chosen with both behaviour and water chemistry in mind:

Congo Tetra (Phenacogrammus interruptus); the classic choice in softer water. Active shoalers that add colour and movement, reduce timidity, and help clean up food particles.
Alestes spp. (African tetras); peaceful midwater shoalers that occupy a similar ecological niche; avoid larger, nippier species.
Small to medium characiforms like Brycinus spp., fast, schooling fishes that stay midwater and are unlikely to be harassed.

Unsuitable companions

Bottom dwellers such as Corydoras, loaches, or Synodontis are risky. While the Mbu rarely attacks deliberately, its clumsy feeding style makes accidental bites likely, and the consequences can be fatal.
Large, territorial, or predatory fish (e.g., cichlids, arowana, tigerfish, peacock bass) are wholly unsuitable. Even if they do not directly injure the Mbu, their behaviour and size are almost guaranteed to keep the puffer in a state of chronic stress.
Other puffers should not be attempted. Intraspecific aggression and accidents are inevitable, especially in confined spaces.

While certain companions can work on paper, the reality is that the Mbu is most successful as a solitary centrepiece. This not only reflects its natural avoidance strategies but also allows the aquarist to focus on providing the vast space, enrichment, and impeccable water quality the species requires. A single Mbu in a dedicated system is often more rewarding, and certainly safer, than any attempt at a mixed “monster fish” display.

Keeping mbu puffer with rays

Pufferfish Enthusiasts Worldwide does not recommend housing Tetraodon mbu with freshwater stingrays (Potamotrygonidae). While this pairing is sometimes attempted in large “monster fish” displays, the risks are significant and very difficult to mitigate.

Behavioural conflicts: Both Mbu puffers and stingrays are benthic-oriented species that interact closely with the substrate. Rays frequently bury themselves, leaving only their eyes exposed. To a curious or hungry puffer, those protruding eyes can resemble snails or other prey items. A single exploratory bite from an Mbu can cause catastrophic, irreparable injury.

Feeding behaviour creates another major conflict. Stingrays are highly food-motivated and feed by swimming over their prey and drawing it into the mouth on their underside. Puffers, by contrast, use their teeth to bite directly into food. In a competitive feeding scenario, an Mbu may become frustrated by a ray intercepting its meal and respond with a defensive or aggressive bite.

Risks of retaliation: A wounded stingray is not defenceless. Freshwater rays carry a venomous barb at the base of the tail which they will use if threatened. A puffer that injures or startles a ray is at real risk of being struck, which could result in severe trauma or death.

Water chemistry incompatibility: Beyond behavioural risks, stingrays are typically soft-water specialists, thriving in acidic conditions (often pH 5.5–7.0, very low hardness). By contrast, Mbu puffers are best maintained in a moderate mid-range (pH 6.8–7.8; GH 5–15 °dGH). Attempting to compromise between these requirements leaves both species outside their optimal range, compounding the risks to long-term health.

Conclusion: While both species are impressive in their own right, combining them creates more hazards than benefits. The potential for disfiguring bites, retaliatory stings, and incompatible water chemistry makes this pairing unsafe. For the welfare of both animals, Mbu puffers and freshwater stingrays should be housed separately.

Stress Pattern

Mbu puffers are highly sensitive fish with body language that clearly reflects their mood and wellbeing. One of the most recognisable signs is their stress pattern, which appears even in response to minor irritation.

When stressed, the normally vibrant green and yellow patterning becomes muted, with colours looking pale or “washed out.” A darkened area develops around the face (often described as a mask), and arched dark bars can be seen running across the back.

This stress pattern may appear briefly during routine aquarium maintenance or if the fish is startled by something outside the tank, such as sudden movement, brightly coloured clothing, or an unfamiliar object. Short-lived episodes are normal and usually nothing to worry about.

However, if the stress pattern is sustained without an obvious trigger, it should be taken seriously. Double-check water parameters, observe the behaviour of any tankmates for aggression, and review the overall environment for possible stressors. Persistent stress can lead to poor health outcomes in puffers, so early intervention is important.

Feeding

One of the defining experiences of keeping an Mbu Puffer is feeding it. These are not casual eaters; they are deliberate, powerful predators whose entire anatomy is designed for crushing, cracking, and dismantling hard-shelled prey.

Watching a Mbu Puffer methodically demolish a crab or grind through a snail shell is to witness one of nature’s most extraordinary feeding machines at work.

In the wild, Mbu puffers forage across their natural ranges, consuming an astonishing range of benthic life. Crabs, freshwater shrimp, crayfish, and snails of all sizes make up the bulk of their diet, but they will also take worms, insects, and even invasive American crayfish that have spread through their range. Their food is diverse, nutrient-rich, and often challenging to access, keeping them engaged as well as nourished.

In the wild, Mbu puffers are active foragers of open river channels, floodplain margins, and lake shallows in the Congo Basin and Lake Tanganyika.

Gut content studies and field observations confirm a diet dominated by molluscs and crustaceans, supplemented by a wide variety of benthic organisms:

Molluscs: Freshwater snails such as Biomphalaria spp. and Melanoides tuberculata, plus unionid clams, form a calcium-rich staple.
Crustaceans: Native freshwater crabs are a major component, including Potamonautes congoensis, P. langi, P. stanleyensis, Acanthothelphusa lirrangensis, and Arcopotamonautes platynotus in Lake Tanganyika. Freshwater shrimp (Caridina spp.) are also taken opportunistically.
Other benthic prey: Worms, aquatic insect larvae, and—in disturbed areas—introduced American crayfish.

This dietary diversity provides nutrition, maintains dental health, and supports natural behaviours such as hunting and shell-crushing.

A captive Mbu should never be restricted to a narrow diet, especially one dominated by thiaminase-rich foods such as mussels or shrimp. Such restriction leads inevitably to nutritional imbalance, poor beak wear, stunted growth, and chronic health decline.

At Pufferfish Enthusiasts Worldwide, we strongly encourage keepers to replicate this natural diversity in the aquarium. Feeding a Mbu is not just about meeting caloric needs; it is about enrichment, nutrition, and welfare. By offering a broad, rotating menu of shelled invertebrates, insects, worms, and prepared diets, we give these puffers not only long, healthy lives, but also the chance to express the captivating behaviours that make them unique.

Suitable Foods

Freshwater crabs and crayfish (frozen-thawed): The core of the diet; always offer shell-on where possible.
Large aquatic and terrestrial snails: Ramshorn, pond, apple, or garden snails (pesticide-free).
Insects: Gut-loaded cockroaches, crickets, locusts, woodlice.
Earthworms: Highly nutritious and excellent variety.
Prepared foods: Repashy (e.g., Grub Pie) and occasional high-quality hard sinking pellet (animal-protein based).
Responsibly sourced cockles: Acceptable in small amounts only, as part of the “miscellaneous” portion.

Recommended Dietary Breakdown (as shown in chart)

60% freshwater crabs & crayfish
20% freshwater snails
10% insects
5% earthworms
5% mixed prepared foods (Repashy, pellets, cockles)

Feeding Practices:

Offer several small meals per day, rather than large, infrequent feedings. This mimics natural foraging, keeps the fish occupied, and aids digestion.
Always size food items appropriately to the fish’s current size: smaller pieces for juveniles, whole shelled items for adults.
Avoid feeding thiaminase-rich foods such as mussels, clams, oysters, etc.

Feeding Enrichment

For a giant, intelligent predator like the Mbu, feeding is not only nutrition—it is the primary source of mental stimulation. Creative feeding methods encourage natural hunting and problem-solving behaviours:

Bury food in substrate: Encourage digging and foraging.
Shell challenges: Provide intact crabs, snails, or cockles to crush.
Food wedged in décor: Place items in crevices to be worked free.
Floating insects: Drop gut-loaded crickets or roaches on the surface to trigger surface strikes.
Scatter feeding: Spread food around the aquarium to promote exploratory behaviour.

These techniques transform feeding into an interactive, engaging experience. A Mbu that must search, crack, and problem-solve at mealtimes is not only healthier and less prone to overgrown teeth, but also more confident and less likely to suffer stress or boredom.

Feeding crayfish and crabs

At Pufferfish Enthusiasts Worldwide, we recommend feeding only frozen-thawed crayfish and crabs to Mbu Puffers.

These prey items form a central part of the Mbu’s natural diet and are among the very best foods for both nutrition and dental health.

Whole, shell-on crustaceans provide the hardness required to wear down the puffer’s continuously growing teeth, while also supplying high-quality protein, fats, and minerals essential for growth and long-term vitality.

Why not live?

Some aquarists argue that offering live crayfish or crabs mimics natural hunting behaviour and adds enrichment.

While this may sound reasonable in principle, the risks greatly outweigh the benefits:

Injury to your fish: Crayfish and crabs defend themselves with sharp claws. Even a large, thick-skinned Mbu is vulnerable to torn lips, open wounds, and—in the worst cases—damaged eyes. In the wild, Mbus frequently carry scars from such encounters, many of which become infected and prove fatal. In captivity, there is no reason to expose them to these risks.
Parasites: Crustaceans are common intermediate hosts for parasites. Feeding them live (without freezing) significantly increases the chance of introducing pathogens to your puffer. Freezing not only prevents injuries but also kills most parasites, making the food far safer.
Welfare of the prey: Some keepers attempt to “disarm” live crayfish by removing their claws before feeding. In practice, this only prolongs the animal’s suffering and raises serious ethical concerns. As responsible aquarists, our duty is not only to the fish we keep but also to the animals we feed them. Minimising unnecessary pain is part of good husbandry.

For these reasons, Pufferfish Enthusiasts Worldwide does not support the feeding of live crayfish or crabs to Mbu puffers.

Best Practice with Frozen-Thawed

Thawing: Select the number of crayfish or crabs you need and thaw them overnight in the refrigerator. Never feed still-frozen prey, as it can cause digestive upset.
Sourcing: Many aquarists purchase freshwater crayfish or crabs in bulk from fishmongers, Asian supermarkets, or wholesale seafood suppliers. Freezing portions in advance is often the most practical and cost-effective method.
Home-breeding: Some keepers choose to breed crayfish at home, euthanising them humanely before freezing. While this offers full control over quality, raising enough to meet the demands of a large adult Mbu is extremely space-, time-, and cost-intensive.
Supply planning: Crustaceans may be seasonal in some regions. A Mbu requires a reliable, year-round supply of shell-on foods, so always confirm your source before committing to keeping one.

Enrichment Without Live Prey

It is true that live prey stimulates natural hunting behaviours. However, the same level of enrichment can be achieved safely:

Offer whole, shell-on crustaceans that require crushing.
Hide food in the substrate to encourage digging and foraging.
Wedge items between rocks or décor, forcing the puffer to investigate and extract them.
Rotate prey types frequently to keep meals varied and engaging.

These safe enrichment techniques engage your Mbu’s powerful instincts without exposing it (or its prey) to unnecessary harm.

Tong Training

One of the most useful and rewarding techniques you can develop with an Mbu Puffer is tong training; teaching it to take food directly from feeding tongs. While it may seem like a simple convenience, tong training is a cornerstone of safe, effective husbandry for a fish of this size.

With tong training, you gain precise control over how and where food is delivered. This is especially valuable with large prey items such as crabs, crayfish, or snails, which can otherwise create mess or be missed entirely. It also allows you to introduce new or less familiar foods in a way the puffer can’t ignore, helping to broaden the diet and keep nutrition balanced.

Over time, Mbus quickly learn to associate the tongs with feeding and will approach them eagerly, often with surprising gentleness for such a powerful animal. For the keeper, this not only ensures accuracy in portioning and food variety but also provides a close, enriching interaction with a fish renowned for its intelligence and personality.

Tong training is more than a technique—it is an opportunity to build trust. Feeding becomes a shared ritual, a moment of cooperation rather than chaos, and a chance to strengthen the bond between keeper and fish while maintaining full control over diet and welfare.

Click here to read our full Tong Training guide.

Filtration and tank maintenance

Mbu Puffers are among the heaviest polluters in freshwater aquaria. Their size, long lifespan, and demanding diet mean they produce enormous amounts of waste.

For this reason, powerful, oversized filtration is non-negotiable. Clean, stable water is not just desirable; it is the absolute foundation of long-term success with this species.

Filtration Requirements

Biological and mechanical strength: An adult Mbu requires filtration capacity far beyond typical aquarium norms. Large, high-quality canister filters, sumps, or even pond-grade systems are strongly recommended.
Redundancy: Many keepers run two or more large filters simultaneously, ensuring stability if one fails and providing extra capacity for the waste load.
Turnover: Aim for a minimum of 6–8x tank volume per hour, with strong flow evenly distributed to avoid dead zones where waste can accumulate.

Good filtration alone is not enough. Mbus require consistent, large-scale water changes to maintain water quality:

Water changes: Carry out at least 50% weekly, and more frequently where possible. In large systems, many successful keepers change 30–40% two to three times per week.
Nitrate management: Keep NO₃ below 15 ppm, and ideally as close to zero as possible. This often means heavy water change schedules paired with careful feeding management.
Debris removal: Mbus produce huge amounts of shell fragments when crushing prey. Always siphon around hardscape and within the substrate to prevent waste build-up and anaerobic pockets.

Why Keep Nitrates Low?

While nitrates are far less immediately toxic than ammonia or nitrite, chronic exposure to elevated nitrate has well-documented negative effects across freshwater species. Long-term nitrate stress can:

Suppress immune function, leaving fish more vulnerable to bacterial and parasitic infections.
Reduce growth rates and feed efficiency, particularly in juveniles during rapid growth.
Shorten lifespan and impair organ health when levels remain consistently high.

For a large, long-lived species like the Mbu, nitrate is not just a number on a test kit, it is a slow-acting stressor that erodes health over years. Keeping levels as low as possible supports stronger immunity, brighter colours, a better appetite, and the decades-long lifespan these remarkable puffers are capable of reaching.

Inflation

Like all puffers, the Mbu has the remarkable ability to inflate when threatened or highly stressed. By rapidly gulping water (or in rare cases, air) it can expand to several times its normal size, making itself harder for predators to swallow.

For such a large fish, this is a dramatic sight, but it is a behaviour that comes at a cost.

In captivity, inflation should never be provoked. Forcing a puffer to puff is extremely stressful, risks physical harm, and can even be fatal. Inflation is a defence mechanism, not a party trick.

Like other large puffers, Mbus occasionally display a behaviour known as “practice puffing.” A relaxed fish may briefly inflate with no obvious trigger before calmly deflating again within seconds. This is thought to exercise the muscles used in inflation and is perfectly normal.

If an Mbu remains inflated for an extended period, however, it is almost always a sign of stress or discomfort. Poor water quality, aggressive tankmates, sudden disturbances outside the aquarium, or an unfamiliar environment can all trigger sustained puffing. The fish will only settle once the underlying problem has been resolved.

Inflation is one of the most iconic behaviours in the puffer world, but in a well-kept aquarium, it should be seen rarely and ideally only as the occasional practice puff of a healthy, confident fish. For an animal as large and long-lived as the Mbu, reducing unnecessary stress is one of the greatest contributions you can make to its welfare.

Toxicity & Toxin Origin

Like many pufferfish, the Mbu (Tetraodon mbu) is believed to accumulate tetrodotoxin (TTX) in the wild through its diet. The fish does not produce this toxin itself; instead, it is thought to originate from certain bacteria associated with the prey they consume. As a result, toxicity levels can vary with location, season, and food availability.

Detailed studies on toxin levels in Mbu puffers have not been published, but research on closely related freshwater puffers shows that toxicity (when present) is usually concentrated in the skin and gonads, and that many individuals test as only weakly toxic or even non-toxic. In some freshwater species, toxin type and intensity can differ altogether, reinforcing that there is no single pattern across the group.

For aquarists, the important point is that Mbu puffers are not considered dangerous in captivity. TTX is a passive poison, not an injected venom, and poses no practical hazard in the aquarium setting. Standard hygiene, such as washing hands after tank work and never consuming the fish, is sufficient precaution.

From a husbandry perspective, toxin biology is an interesting scientific footnote, but it has no impact on day-to-day care.

We would like to give a special thanks to Katjana, Moderator of Pufferfish Enthusiasts Worldwide and keeper of @barry_thepuffer, who kindly submitted their photos for this care sheet.