Pufferfish are probably the most popular oddball aquarium fish, though the range of species sold is actually quite limited. Three Asian species, and one a piece from Africa and South America dominate. The Asian species are all brackish water fish and need to be kept with other brackish water fish. These are the green spotted puffer, Tetraodon nigroviridis, the very similar topaz puffer, Tetraodon fluviatilis, and figure-eight puffer, Tetraodon biocellatus. The other two pufferfish that you are most likely to encounter are the giant African puffer, Tetraodon mbu, and the South American puffer, Colomesus asellus.
These are, however, far from the only ones freshwater and brackish water puffers traded. Indeed, over the last few years the diversity of freshwater pufferfish offered to aquarists has steadily increased, and in this article, we'll look at some of these fish are review their basic requirements and habits.
The dwarf puffers, genus Carinotetraodon
This genus of pufferfish includes a number of small, strictly freshwater pufferfish from South and South East Asia. Apart from their size, the most characteristic feature of this genus is pronounced sexual dimorphism: the makes are usually much more brightly coloured and invariably posses erectile ridges along the belly and back. In fact, the scientific name of the genus, Carinotetraodon, comes from these structures, karina meaning 'keel' in Greek. When males are displaying to females, or threatening one another, they raise these keels, presumably to make themselves look more imposing. Both sexes can puff themselves up in the normal manner when alarmed, just like other pufferfish.
Although Carinotetraodon spp. are territorial and snappy towards one another, like most other pufferfish, their small size makes it possible for multiple specimens to be accommodated in a sufficiently large aquarium. Under such circumstances, males and females will eventually pair off, and following some fairly rough courtship behaviour they will spawn, often in a thick mass of Java moss. The male will then drive off the female and guard the eggs until they hatch, which normally takes about three days. Once the fry are free swimming, after another couple of days, they will accept tiny lived foods, such as microworms, and after a week or two they can be weaned onto newly hatched brine shrimp and small Daphnia.
There are three species of Carinotetraodon regularly traded, of which the most common is probably Carinotetraodon travancoricus, an Indian species often simply called the dwarf puffer. It is indeed a tiny fish, barely 2 cm long when mature, and a densely planted 40-litre (10 gallon) aquarium will comfortably house a single make and three females without much risk of aggression between them. Unfortunately, males and females are very similar when young; so sexing the fish in your retailer's tanks is difficult. However, once mature, sexing them is quite easy: while both fish have a dark band along the ventral surface, the male's is much darker. Males may have stronger overall colouration as well, particularly when spawning, but this is an unreliable indicator because there is so much variation in the colouration of these fish anyway. Besides variation between specimens, individual fish can also change their colours depending on their mood.
Carinotetraodon travancoricus are confirmed fin-nippers, and keeping them with tankmates such as small tetras or barbs is a bit of a gamble. On the other hand, they generally get along well with dwarf suckermouth catfish (Otocinclus spp.) and freshwater shrimps (Caridina spp.). As far as feeding goes, these fish are very adaptable, and will take all kinds of live and frozen foods, including small snails, bloodworms, clean Tubifex worms, and Daphnia. Brine shrimp are a good treat and willingly taken, but their nutritional value is low so they shouldn't be used as a staple. One nice thing about Carinotetraodon travancoricus is that it is predominantly day-active, and is in fact remarkably outgoing given its size. It is also very tolerant of water chemistry, doing equally well in both slightly soft and acidic conditions and moderately hard and alkaline ones. As with all pufferfish though, it does not appreciate rapid changes in pH and hardness, and is very intolerant of nitrite and ammonium. Provided they are kept in a well-filtered, mature aquarium, these are lovely fish, and excellent oddballs for the aquarist with only limited space.
Less commonly encountered is the red-eye puffer, Carinotetraodon lorteti. Found throughout much of South East Asia it has been known to the hobby for decades, often being traded under an old name, Carinotetraodon somphongsi. Though well know, its availability has been patchy, almost certainly because its high level of aggression and persistent fin nipping make it impossible to keep in a community tank. In terms of basic requirements, this species is comparable to the dwarf puffer in most respects, though being a larger fish it does need a bigger aquarium. A matched pair may be housed in a 40-litre (10 gallon) aquarium. Males are easily distinguished from females by their colours; males are basically brown with mustard yellow stripes across the head and back. The belly is cream-coloured belly except for a reddish stripe across the keel running from just behind the mouth to the base of the anal fin. The tail fin is greenish-blue and fringed with a thin white band. Females are attractive but in a different way, sporting a mottled pattern of light and dark brown above and off-white below. Both sexes sport red irises, from which comes their common name.
The least widely seen of the three popular Carinotetraodon species is the red-tail puffer, Carinotetraodon irrubesco. It is sometimes muddled up with the red-eye puffer, and females of the two species are virtually identical, the only obvious difference being that female Carinotetraodon irrubesco bear thin brown stripes on the belly that female Carinotetraodon lorteti lack. Male Carinotetraodon irrubesco can be immediately recognised by their red tails, but they also have red dorsal fins and the lighter bands on the dorsal surface are tan coloured rather than yellow. While it is a toss-up which of the two species is the more attractive, Carinotetraodon irrubesco definitely has the advantage as far as personality goes. It is relatively peaceful and can be kept with a variety of other fish, provided slow moving species with long fins are avoided. My own species seem to get along well with cardinal tetras, gobies, Otocinclus, and juvenile halfbeaks.
Two additional species of Carinotetraodon are traded very occasionally, the Borneo red-eye puffer, Carinotetraodon borneensis, and the banded red-eye puffer, Carinotetraodon salivator. Male Borneo red-eyes are similar to C. lorteti but the with greenish-yellow banding instead of bright yellow and they also have a distinctive blue tail. Female Borneo red-eye puffers are essentially identical to female C. lorteti, though the colour banding on the back may be a trifle more yellowy. Banded (or striped) red-eye puffers are easy to recognise because of the vertical banding on the head and body. These bands vary in intensity, being most obvious on spawning males, but even on quiescent males should be apparent. Female striped red-eye puffers look a lot like female Carinotetraodon irrubesco. Unfortunately, males of these two species are extremely aggressive, both towards females and other fishes in the aquarium. Aquarists intent on spawning these fish, should they be lucky enough to obtain them, will almost certainly need to condition the female apart from the male, and only introduce the male when she is carrying eggs. Even then, there are no guarantees that they will spawn, and separating the fish if things turn nasty will be essential.
The fugu puffers, genus Takifugu
The Takifugu spp. puffers are important primarily as food fish rather than aquarium fish, with several being cultured on fish farms or caught in the cool waters off China, Korea, and Japan to supply discerning gastronomes with the famous fugu. As is well known, fugu requires careful preparation, because some of the internal organs of the fish contain a deadly poison, tetrodotoxin. Takifugu puffers are also widely studied by biologists because they have remarkably small genomes, making it much easier for scientists to study their entire sequence of genes than is the case with most other vertebrate animals. Humans, for example, have a genome about seven times larger, and even that of the humble danio is more than four times larger than that of Takifugu rubripes.
Most likely as a by-product of the abundance of these fish in the aquaculture industry, a handful of Takifugu puffers are now appearing in aquarium shops with some regularity. The peacock puffer is particularly common, and being brightly coloured and not too large, it would seem to have great potential. However, it does have the reputation for being rather delicate, with many aquarists considering it impossible to keep alive. At least part of the problem would seem to be inappropriate water conditions: these are subtropical fish that normally live in estuaries. They cannot be kept in freshwater aquaria indefinitely, and they should only ever be kept in relatively cool aquaria. A water temperature of 18-20Ë°C (64-68Ë°F) is ideal. A higher temperature reduces the amount of oxygen in the water while increasing the metabolism of the fish, the result being a fish that dies from slow asphyxiation.
Besides temperature, the other big issue with these fish is water chemistry. All Takifugu live in marine habitats, either in the open sea or in coastal waters and estuaries. At least two species are known to spawn in freshwater though, Takifugu obscurus and Takifugu ocellatus, and as a result these species are sometimes traded as freshwater fish. While they can survive in fresh water for months, perhaps longer, both will be much healthier if kept in at least brackish water. Takifugu ocellatus should be maintained in brackish water at a specific gravity of about 1.010-1012, while Takifugu obscurus can be kept either in similar brackish water conditions or in normal seawater. Takifugu niphobles is best considered only a temporary resident of fresh or brackish water, and needs fully marine conditions to do well over the long term.
Takifugu ocellatus is the most widely seen of the two species. It is easily recognised by its vivid colouration: it has a metallic green body with bright orange markings on the back between the pectoral fins and at the base of the anal fin. In terms of behaviour, this species is unpredictable. It is not a fin-nipper, at least, but it can be aggressive towards conspecifics. Because it needs subtropical conditions, standard brackish water fish from warmer waters do not make ideal tankmates. One exception is Scatophagus argus, which ranges north into Takifugu ocellatus territory, and the two might be maintained at 20Ë°C (68Ë°F) without problems.
Takifugu obscurus is a much less attractive fish but is, perhaps, a better bet for the home aquarium. It has a greyish silver body with a yellowy band running from the mouth along the flanks to the base of the tail. Above and slightly behind the pectoral fin is a large black eyespot ringed with pale grey; the belly is off-white. Like Takifugu ocellatus, this is a euryhaline species that lives in the sea but breeds in fresh water. Juveniles are believed to live in rivers for about a year before swimming downstream to mature in the open sea. Takifugu niphobles is a similar species and can be confused with Takifugu ocellatus, having a similar black patch behind the pectoral fin. Its body is a much darker grey though, and the entire upper surface is peppered with small white spots. A giant among pufferfish, it can reach lengths of up to 80 cm, but even specimens only half as large will still require massive quarters with excellent filtration. All in all, not an ideal aquarium fish, despite the fact that it has proven to be quite hardy and easy to care for.
Two Asian freshwater puffers
Over a dozen species of Tetraodon have been imported as aquarium fish, though as mentioned earlier, only a few have become staples of the hobby. Besides the species mentioned about, Tetraodon lineatus, the fahaka puffer, and Tetraodon miurus, the Congo puffer, are both regularly, if infrequently, traded. One newcomer to the hobby actually has quite a familiar name, Tetraodon palembangensis. For many years, figure-eight pufferfish were sold under this name, and many aquarium books continue to describe them as such. In fact, Tetraodon palembangensis is a quite separate fish, and a freshwater rather than brackish water species to boot. Known under a variety of names include 'humpback puffer' and 'dragon puffer', this is a fairly large, piscivorous species distinguished by its very unusual shape. Where most puffers have a flat or slightly arched back, this species has an almost triangular back, giving the fish the appearance of having a deformed spine. It is also somewhat flattened from top to bottom and has a distinctly upturned mouth. The result is a terribly ugly, or wonderfully endearing fish, depending on your tastes.
Tetraodon palembangensis is a predatory, territorial species that is best kept on its own. Given its 20 cm adult size, a single specimen probably needs a 180-litre (40 gallon) aquarium, and should either be kept alone or possible with some type of armoured catfish. Aggression towards conspecifics is limited to threats and the odd bite, but provided the aquarium is sufficiently roomy and the fish have plenty of hiding places -- thickets of robust plants are ideal -- the fish will settle down and tolerate one another. Feeding presents few problems, as they can be weaned onto a variety of dead foods, including bloodworms, prawns, and mussels. Live river shrimp, snails, and earthworms can also be used as well.
Tetraodon suvattii, the Mekong puffer, is very similar in habits to Tetraodon palembangensis, though it is a bit smaller and doesn't have such a humped back. It is a piscivore, and while not especially aggressive, it cannot really be combined with anything except others of its own kind. Even with conspecifics, territorial aggression can flare up, especially when the fish become mature and think about spawning. This species has, incidentally, been bred in home aquaria a number of times. As with other puffers, the male guards the eggs, and the fry, once free swimming, are fairly large and can take newly hatched brine shrimps at once. Both the humpback puffer and the Mekong puffer are rather inactive fish that spend most of their time hidden in caves or among the leaves of large plants.
Our final newbie pufferfish is Fang's puffer, Tetraodon cochinchinensis. A waspish fish, it is a confirmed nipper and cannot be kept in a community tank despite its small size. Some aquarists have kept these fish in groups, but they are very territorial, and will attack any conspecifics that swim by their lair. Under such conditions this species can be spawned, and some of the specimens sold now are said to be tank bred, but even so, it is most easily kept on its own in a 90-litre (20 gallon) tank. When not feeding or fighting, these fish are barely more active than humpback or Mekong puffers, and mostly just hide inside their chosen cave.
These new pufferfish are not for everyone, but if you can work around their specific needs, these could be very interesting and rewarding fish. The dwarf puffers in particular, and perhaps Fang's puffer as well, are small enough that their antisocial behaviour can be easily accommodated by simply setting up another aquarium just for them. That so many of these smaller species are breedable makes them even more tempting. All pufferfish are demanding though, needing tip-top filtration and frequent water changes, but if you can provide the care they need, these are fish you are sure to enjoy.
Scientific name: Carinotetraodon irrubesco
Common name: Red-tail puffer
Maximum size: 4.5 cm
Distribution: Sumatra and Borneo
Habitat: Densely vegetated areas in slow-moving waters
Remarks: Very shy but fairly peaceful and only rarely nips the fins of other fish
Scientific name: Carinotetraodon lorteti
Common name: Red-eye puffer
Maximum size: 5.5 cm
Distribution: Widely distributed across South East Asia
Habitat: Densely vegetated areas in slow-moving waters
Remarks: Though shy, this species is aggressive and a confirmed fin-nipper
Scientific name: Carinotetraodon travancoricus
Common name: Dwarf puffer
Maximum size: 2.5 cm
Distribution: Southern India (Kerala)
Habitat: Shallow, weedy parts of the River Pamba
Remarks: Relatively tolerant of one another and other tankmates, but still a potential fin-nipper
Scientific name: Takifugu rubripes
Common name: Tiger puffer
Maximum size: Up to 80 cm
Distribution: China and Japan
Habitat: Juveniles live in shallow waters including estuaries and freshwater rivers, but adults live in the sea
Remarks: A subtropical species, robust, but given its large size, needs a very big aquarium
Scientific name: Takifugu obscurus
Common name: Tiger puffer
Maximum size: Up to 40 cm, but usually much smaller
Distribution: China and Korea
Habitat: Spawns in freshwater, adults live in the sea
Remarks: A subtropical species, but hardy are relatively easily maintained
Scientific name: Takifugu ocellatus
Common name: Peacock puffer
Maximum size: 15 cm
Distribution: Pacific coastline of Asia, from Vietnam to southern China
Remarks: A delicate, subtropical species that dies quickly if kept in a tropical aquarium
Scientific name: Tetraodon palembangensis
Common name: Humpback puffer
Maximum size: Around 20 cm
Distribution: South East Asia
Habitat: Freshwater rivers
Remarks: Inactive, somewhat aggressive loner
Scientific name: Tetraodon suvattii
Common name: Mekong puffer
Maximum size: Under 15 cm
Distribution: Mekong River, Thailand and Laos
Habitat: Freshwater rivers
Remarks: Inactive, territorial species likely to attack tankmates other than its own kind