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 is probably the most famous species of freshwater pufferfish. It belongs to the Tetraodon genus, which has a total of six species, including the lineatus (Fahaka) and schoutedeni.
The Tetraodon mbu can easily achieve lengths of 75cm + (approximately 30 inches) making it the largest species of freshwater pufferfish in the world.
Common names for this species include Giant Puffer, Giant Congo Puffer, and Tanganyika Puffer, but it is most widely known to aquarists as the Mbu Puffer.
In the wild
They can be found in rivers and lakes (including Lake Tanganyika) across the Republic of Congo, Democratic Republic of Congo, Tanzania, Zambia, Burundi and Cameroon. The mbu puffer typically lurks around submerged vegetation and avoids areas of open water within its natural habitats.
They prey predominantly on snails, freshwater crabs, insects and other benthic creatures.
The Tetraodon mbu is not bred commercially so all specimens available for sale are wild-caught.
Wild-caught juvenile Tetraodon mbu are reasonably common in most areas of the world. Collection for the aquatic trade is not considered a threat but the number of individuals taken from the wild or the size of wild populations is not known.
The Tetraodon Mbu was assessed in 2009 and the IUCN (International Union for Conservation of Nature) classifies the species as 'Least Concern'. However, changes in habitats due to human activity (agriculture, aquaculture, and pollution) may threaten the species in future.
According to several sources, the mbu puffer is also harvested for human consumption.
In the aquarium
The Tetraodon mbu is a large and intelligent species of pufferfish, so it requires a very big aquarium with a complex and enriching scape design to keep it occupied.
This pufferfish avoids open areas of water in its natural habitat because it feels too exposed and the same is true in aquariums, so the tank must offer the pufferfish areas in which it can take cover.
This is especially important in young mbu puffers or newly imported adults. A busy scape will help them feel more safe and secure, and their confidence will grow in time.
You can give an enriching aquarium by providing an elaborate scape with lots of caves and hiding spaces to explore, but keep their size in mind and maintain plenty of open swimming space too. You can heavily decorate a tank for a juvenile and then enlarge the open areas as the fish grows.
An appropriately scaped tank will help the large yet shy mbu puffer feel secure and confident, knowing that it can take cover quickly if needed which will result in more assertive and explorative behaviours.
The flow in the aquarium should be medium to strong, but never overpowering. The strength of the flow is usually adjusted with spray bars angled towards the top of the water. Keeping a slightly dropped water level, so that the returning water from the filter splashes down onto the surface, it will create the agitation required whilst also facilitating gas exchange for high levels of oxygenation.
Wavemakers with narrow gaps in the grill may be used to create additional flow. We would advise that cages or guards (such as anemone guards) be used on wavemakers to prevent injury to the fish if they become trapped.
Avoid any exposed power cables into the aquarium as mbu puffer can easily bite through them.
With the correct care, a mbu can live in excess of 20 years.
A fish that lives for 20+ years will be with you through a lot of changes in your life, so these fish obviously represent a long-term commitment.
Substrate
The Tetraodon mbu is a wallowing species of pufferfish and should always be provided with a substrate that allows it to indulge in this natural behaviour.
A usable substrate is a critical component of enrichment for this fish. They wallow for several reasons, such as to hunt, to avoid the detection of bigger predators (who might eat them), or simply just to safely rest.
Pufferfish dig into the substrate by nose-diving the ground and using their powerful tails to push their whole body forward into the substrate. If the substrate is too hard or abrasive then it may cause scrapes and scratches which could be painful for the fish and predispose it to bacterial and/or fungal infections. Fungal and bacterial organisms will take full advantage of even minor abrasions, so it is important that we do everything we can to prevent such injuries. As a general rule, fine sand is the best option for any wallowing species of pufferfish. The softer/smoother the sand is, the better for the pufferfish.
Play sand or Pool Filter sand can also be used, providing that it is fine enough and doesn't contain any potentially harmful chemicals. Gravel and plant-soil/substrates are unsuitable for the Mbu and may cause injury if the Mbu attempts to wallow in it. Any sharp or coarse pieces should be avoided/removed.
You can read more on suitable substrates here: What is the best substrate for wallowing pufferfish?
The depth of the sand should always match the depth of the fish's body. It is recommended to start as shallow as possible and then gradually increase the depth of the substrate as the fish grows. This fish will disturb the substrate on a regular basis by moving from place to place within the sand, but it is recommended that the keeper regularly stirs up the substrate to stop the sand from ‘compacting’ to prevent the build-up of anaerobic bacterial populations. The depth of substrate required for an adult mbu puffer will need stirring at least once a week.
The mbu can adjust their colouration to better blend in with their surroundings. We recommend using paler substrates which will encourage the fish to display its most visually appealing colouration.
Bare-bottomed / Tile-bottomed Tanks
Some keepers may choose a bare-bottomed or tile-bottomed aquarium because they feel they are easier to keep clean or may find it more visually appealing for themselves, but the primary concern when designing an aquarium should always be the welfare of the animals that you intend to keep in it.
Bare-bottomed tanks deny a wallower the opportunity to express its natural behaviour and the keeper should never elect to deprive an animal of crucial enrichment.
A mbu puffer is healthiest and happiest when they are given a suitable substrate.
Pufferfish Enthusiasts Worldwide will always encourage naturalistic aquariums that make the animals feel right at home.
The only time bare-bottomed tanks should be considered is during the initial quarantine or during worming treatment.
Tank size
Mbu puffers are big, active fish which can achieve lengths exceeding 75cm (approximately 30 inches), so of course, they should be housed in very large aquariums.
Pufferfish Enthusiasts Worldwide recommends a tank no smaller than 8x3x3 (96"x36"x36") for a mbu puffer. This translates to a tank volume of approximately 2,040 litres / 540 US gallons.
The dimensions of the tank are the most important facet of suitability, not the amount of water it can hold. An eight-foot tank is only just over 3x the length of a fully grown, healthy mbu puffer and the 3 feet depth (front to back) only just allows a 30" fish to turn around within and change its course; so we are sure you can appreciate why we would not want to go any smaller than this.
We would like to stress that an 8x3x3 tank is what we consider as the absolute minimum for this fish and that bigger always equals better. The tank should be at least 25% larger for every additional mbu puffer you wish to add.
Aquariums which are large enough for an adult mbu puffer are very rarely available off the shelf and will not fit through standard domestic doors. This forces most keepers to have a tank custom-made and then assembled in the house. Custom tanks are often very good value for money and allow you to fully specify the exact dimensions that you require, but they are expensive and this is something that you need to very carefully consider before taking on the massive responsibility that mbu puffers represent.
Falsehoods about the size of captive mbu puffers
We would like to challenge the common falsehood that captive mbu puffers are incapable of growing as large as wild specimens, so such large tanks are not required.
In actual fact, mbu puffers (like most fish) should have a better chance under captive management of achieving their full potential size than wild ones and should also live for a significantly longer time.
Under good husbandry, the mbu puffer should be receiving optimal nutrition through a steady supply of high-quality foods - without the seasonal famines that they would experience in the wild - and the parasites that compete with the fish for nutrients and other resources (which would go unchecked in the wild) can be completely eradicated in captivity. The water quality in their aquariums should be excellent, with no pollutants, there should be no harsh climatic conditions for the fish to deal with, and diseases can be treated quickly.
Your mbu puffer should also be significantly less stressed in captivity because they should not have any food competition, territorial fights with other fish and the risk of predation would be completely removed. It is well known that fish who experience less stress enjoy lower metabolic rates, more energy and stamina, can better absorb the nutrients they consume and are able to better spend that energy on growth and development.
When conditions are not optimal, the fish have a lower chance of achieving full size.
It is not captivity that stunts the growth of fish. It is the traditionally poor husbandry that so many mbu puffers have received which stunts the growth that has led to the myth that they are incapable of growing so large.
Tankmates
Although the mbu puffer is considered to be one of the most 'peaceful' pufferfish species by many in the trade and hobby, tankmates must still be very carefully considered.
The mbu is a very sensitive and easily stressed species of puffer, despite its large size.
It normally avoids conflict with other fish at all costs, especially those who are bigger than itself. It is therefore not suited to the typical predatory tank.
Many of the larger species of fish that are found in the mbu's natural habitat are either very aggressive and territorial (eg Boulengerochromis microlepis), or piscivorous.
The mbu has learned through natural selection that it is best to give large fish a wide berth and will do its best to evade them. It has an inbuilt instinct to avoid large fish and this instinct helps keep the mbu puffer safe and it doesn't disappear when the fish are in captivity.
For these reasons, we strongly discourage owners of the mbu to keep it with any fish which are aggressive/boisterous or territorial, are bigger than it is, or will frequently swim above the puffer's head. Large fish who occupy the higher regions of the tank can make the mbu puffer nervous and this may encourage the mbu to stay within the lower regions of the aquarium in order to avoid them.
We really recommend that your mbu puffer remains the centrepiece of the aquarium, being the largest fish in there and that any tank mates are peaceful, non-territorial, and not too fast a swimmer.
If your water is below 15gh hardness, then the medium-sized Congo Tetra (Phenacogrammus interruptus) can make wonderful tank mates. They will act as a nice dither fish, which will both reduce timidity of the mbu and enhance the viewing experience for the keeper by shoaling in the aquarium.
Congo Tetras are small enough not to compete with the mbu puffer for food, but they are food-driven enough to follow the mbu and collect the small particles of food which the puffer will create when it chews its own food.
This species of pufferfish should not be housed with any bottom-dwelling fish, such as corydoras, who may surround the puffer's food on the substrate. Although it is unlikely that a mbu puffer would intentionally injure one of these fish, it is very possible that the mbu puffer will accidentally bite them.
Mbu pufferfish have powerful bites and can inflict serious injuries on other fish very easily, whether intentional or not.
Keeping mbu puffer with rays
Pufferfish Enthusiasts Worldwide does not recommend that the Mbu puffer be kept with freshwater stingrays. Species of ray can bury themselves in the substrate, similar to how pufferfish do and for many of the same reasons, and they may almost completely conceal themselves with only their eyes protruding from the substrate. Those eyes can closely resemble a tasty snail to a hungry or curious mbu puffer who might not distinguish the difference and take a bite of the eye.
Stingrays are also very food motivated animals and they swim above their food, eating it with their mouth which is on the underside. A mbu puffer could become frustrated with a ray that is between it and the food that it perceives as theirs, and may choose to bite the ray.
Both of these scenarios could result in a catastrophic injury for both the ray and the mbu puffer, as the ray will likely defend itself with the venomous barb that they are equipped with on the base of their tail.
Additionally, freshwater stingrays typically have water hardness requirements that are much lower than that of the mbu puffer.
Water values
Maintain the following water parameters:
PH: 7.0 - 8.0
Temp: 24 - 26°C (71.6 -78.8°F)
Ammonia (NH3): 0ppm
Nitrite (N02): 0ppm
Nitrate (N03): below 15ppm
GH: 8-25 dGH
Notable behaviour
Mbu puffers are very sensitive creatures and they have a distinctive stress pattern that can be seen in even slightly irritated specimens.
When the mbu is stressed and displays the stress pattern, the green and yellow areas will appear washed out with a darkened area around the face (commonly referred to as a mask) and dark bars which arch across the back.
A mbu puffer may display the stress pattern during aquarium maintenance or if it has been spooked by something outside of the aquarium, like brightly coloured clothing or an unfamiliar object. If this behaviour is sustained and there are no obvious causes, check the water parameters and observe any other fish in the aquarium for signs of aggression.
Feeding
The majority of the mbu puffer's natural diet consists of the crabs, shrimp, and snails - of all sizes - that are found in their natural habitat. Other components include worms and other benthic creatures.
Mbu puffers also eat the several species of American crayfish that are now an invasive species in their natural habitat.
Pufferfish Enthusiasts Worldwide will always encourage keepers to replicate the natural diet of their pufferfish as closely as possible. Wild mbu puffers eat a very diverse range of prey and it is your responsibility as a keeper of a captive mbu to provide as many different kinds of appropriate foods as possible.
Aside from providing a variety of flavours and textures for food enrichment, a varied diet of suitable foods will supply a greater spectrum of nutrients to your fish that are essential to the health, growth, development and long lifespan of the mbu puffer.
The following diet suggestions and food items are suitable for mbu puffers of all ages and sizes, but portion and food item size needs to be modulated to suit the size of the fish.
Suitable foods for this species include:
Frozen-thawed freshwater crabs
Frozen-thawed crayfish
Large terrestrial and aquatic snails
Insects including Gutloaded cockroaches, crickets, locusts and woodlice
Earthworms
Repashy foods - eg GrubPie
A high-quality, hard pellet food (protein not derived from vegetable sources)
We suggest breaking down the diet (as shown in the chart) to approximately 60% freshwater crabs & crayfish, 20% freshwater snails, 10% insects, 5% earthworms, and a 5% mix of foods such as Repashy and a high-quality pellet food (preferably sinking pellet).
Responsibly sourced cockles can be fed, but should not be offered in any great portion and within the suggested 5% mix of food.
It is best to feed several small meals throughout the day rather than offering larger, less frequent meals. This helps keep the pufferfish occupied throughout the day and allows the fish to digest smaller portions.
This species should not be offered krill, mussel, clams, or oysters. Unsuitable foods can result in stunted growth and poor health.
Feeding crayfish and crabs
Pufferfish Enthusiasts Worldwide recommends feeding only frozen-thawed crayfish and crabs.
We strongly discourage keepers from feeding live crayfish and crabs for the following reasons;
It is true that these pufferfish are hunting live crayfish and crabs in the wild and there is an argument that hunting live food offers your puffer a level of enrichment that it does not receive through eating frozen-thawed. However, we believe that the risks greatly outweigh the benefits.
Very few things enjoy being eaten by pufferfish; crayfish and crabs definitely fall into the category of things that don't want to be devoured. They will try to defend themselves using their sharp claws, which can easily injure your puffer.
Whilst these fish may have thick skin, we often see puffers with injured lips, cuts on their body and even missing/damaged eyes from where a live crayfish or crab has tried to defend itself. Wild mbu puffers often suffer from hunting injuries, many of which become infected and prove fatal for the fish.
Some keepers opt for removing the claws from live crayfish and crabs before offering them to the pufferfish, however, this practice raises some serious ethical questions as mutilating the animal prior to throwing it in to be chased, crushed, and then chewed maximises that animal's suffering. It should be our primary objective as responsible and ethical keepers of predatory fish to ensure the welfare of not just the fish we keep but also that of the prey they eat by minimising the pain and suffering as far as reasonably possible.
Things that do enjoy being eaten by pufferfish are the parasites that use crustaceans as intermediate hosts and will then infect your fish upon being consumed. Feeding crayfish and crabs that have not been frozen significantly increases the chances of introducing these parasites to your puffer. Dead organisms obviously can't fight back and as the freezing process kills the parasites, feeding frozen-thawed eliminates both the risk of injury and parasite transfer.
Frozen crayfish and crabs must be thawed before feeding to your mbu puffer. Select the amount of prey that you wish to feed out of the freezer and thaw it out in the fridge the night before.
Some members of PEW breed their own crayfish at home then euthanise them prior to freezing. This is a convenient method for some keepers, but it should be noted that raising enough crayfish to meet the demands of a fully grown mbu puffer can be very finance, space and time-consuming. Typically, the cheapest and easiest procurement of crayfish and freshwater crabs is buying them in bulk from fishmongers and Asian supermarkets.
Whatever you decide to do, it is a good idea to check the availability of these food items; if that supply is reliable or subject to seasonal availability, ensure that you will be able to maintain their required diet all year round.
Filtration and tank maintenance
This pufferfish is intolerant of poor water conditions, so a high level of biological and mechanical filtration is needed to deal with the amount of waste that this fish produces.
Good filtration combined with excellent husbandry is essential to the health of this species. Frequent water changes must be carried out to maintain NO3 (nitrate) levels below 15ppm; or as close to zero as possible.
We recommend a minimum water change of 50% every seven days on appropriately sized tanks.
Inflation
The mbu puffer can inflate themselves when frightened or stressed.
They should never be provoked into inflating!
It is common for this species to "practice puff", which is when the fish casually inflates itself for no apparent reason. It is believed that they do this to stretch and strengthen the muscles associated with inflation.
"Practise puffs" are usually very short-lived. If your puffer remains inflated, investigate for sources of stress.
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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.
