Charming and unusual, the pufferfishes and porcupinefishes are considered by nearly all aquarists of all types. Their wide availability can certainly be taken as some measure of their popularity. Nevertheless, despite their apparent familiarity in the hobby, they have widely ranging husbandry requirements and frequently have a diet and/or temperament that excludes them from the conventional “community” tank. In short, any aquarist who wishes to keep these animals should be well informed of the specific care required for each species they want to keep. While such detailed information is beyond the scope of this discussion, it is hoped that the following overview not only provides a practical starting point for one’s research, but also engenders a greater appreciation and respect for the group.
History and Background Info on Puffers and Porcupine Fish
Pufferfishes and porcupinefishes share the order Tetraodontiformes with the triggerfishes, filefishes, boxfishes and their relatives. The tetraodontiforms (or plectognaths) include around 300 species from eight families. Though incredibly diverse, this broad group can be characterized as having modified scales that serve as plates or spines with resultantly restricted gill openings. Both puffers and porcupines lack pelvic fins (and, in some cases, pelvic bones).
The puffers (family Tetraodintidae) may be found in fresh, brackish or marine waters and are widely distributed across tropical and temperate regions. They more or less lack scales, with only some prickles on the underside of the body. As their family name would indicate, they have four strong, fused teeth set into their jaws. Among the most popular members of the family are the decidedly smaller and more colorful puffers of the genus Canthigaster (i.e. the sharpnose puffers).
The porcupinefishes (family Diodontidae) are also fairly well distributed, albeit restricted primarily to the inner sublittoral zones of warmer seas. While roughly similar to the puffers in overall form, the porcupines bear well-developed burrs or spines on the skin. This group has just a pair of fused teeth in the jaws. Undoubtedly, the most popular and recognizable representatives of the family belong to the genus Diodon (i.e. the balloonfishes).
The aptly named three-toothed puffers (family Triodontidae) are known as having only a single representative, Triodon macropterus. The species is placed into its own family not only because of its trio of fused teeth but also for its unique configuration of anal and dorsal fin rays.
Puffer Fish and Porcupine Fish Defenses
Puffers and porcupines have two very interesting and well-known defenses. Firstly, most puffers and porcupines have the ability to inflate their bodies. This is accomplished through the rapid uptake of water or air into an internal sac. This sac either lines the stomach or some part of the stomach; it is not related to or derived from the swim bladder. Through signals that are sent when the animal is seriously threatened, various sphincters in the sac open up to rapidly fill the sac and distend the body into a much larger, globular shape. During inflation, the walls of the sac may be stretched paper-thin. The spines or burrs of porcupines become erect while the animal is inflated. Deflation is similarly under control of the sphincters, with the assistance of the abdominal muscles. Once deflated, a threatened animal will usually flee to a safer area.
The second notable defense of these fishes is toxicity of the flesh (i.e. ichthysarcotoxicity). Some believe the toxin to be obtained by the fish from the dietary consumption of certain marine plants. Toxification of the flesh of puffers, porcupines and their boxfish cousins results in ciguatera-like poisoning. The flesh is poisonous only if eaten. The affliction is fatal to about 7% of cases involving humans.
Puffers and porcupines clearly sacrifice some degree of motility for their bulbous body shape. Moreover, their rather stiffened skeletal structure and bony gill covers can impede respiration. They compensate for this burden through a compensatory respiration rate that is driven by rapid breathing. These fishes may make as many as 180 gill beats per minute.
Tetraodontids and Diodontids in the Aquarium
Few would argue that the puffers and their allies are incredibly amusing creatures. Some of these endearing qualities have led to many misconceptions about their aquarium care that has led to countless injuries and mortalities. Perhaps the biggest mistake aquarists make is in taking these animals’ aggressiveness for friendliness. Endowed with highly effective defenses, puffers and porcupines have a distinct lack of fear that too many keepers interpret as an innocent, puppy-like inquisitiveness. To be sure, this often brutish fish is quite willing to use its powerful jaws and teeth to inflict injury not only upon its tankmates but also its keeper. A sad but all too widespread reminder of this tendency are the wounds and shredded fins of fish that they are housed with in disreputable dealers’ display tanks. Even spiny or shelled invertebrates (e.g. clams, sea urchins) are not safe from these voracious carnivores, as they may crunch through practically anything with their beak-like teeth. Indeed, some keepers have found that unless there is adequate material present for the fish to grind its ever-growing teeth on, overgrowth can occur, requiring veterinary dentistry to remedy.
Adult size should always be considered when selecting puffers and porcupines. Some favorites such as the blowfish (Diodon hystrix) and the stars-and-stripes puffer (Arothron hispidus) can quickly grow to exceed 50 cm in length. This is significant particularly because these fishes—at any size—require a considerable amount of free space. While it is imperative that they have access to some rock and shell to grind, they should also have a large volume of open swimming space. Some authors suggest a tank of at least 600 liters for some of the larger species. The tank should be equipped with a similarly oversized filter system; this will not only be needed to cope with the puffer’s large waste output, but will also ensure that the water is well aerated as to minimize any respiratory stress to the animal.
The processes of inflation and deflation are actually quite stressful and physically taxing for the animal; needless to say, these fishes should never be made to blow up for mere amusement.
Good and Bad Tankmates for Puffer Fish
Tankmates should be especially robust and aggressive. Even from among these types, puffers should not be trusted with slow-moving or bottom dwelling species that can be easily nipped at (e.g. many sharks and lionfishes). Appropriately sized groupers and wrasses, for example, can make great companions.
What do Puffer Fish and Porcupines Eat?
Puffers and porcupines are omnivores with big appetites. Consequently, they are easily fed any kind of meaty food (silversides, squid, prawn, etc.), but also generally cannot be kept in most reef tanks. So few invertebrates are safe with these fishes that it is best to commit to having none at all. Some brave hobbyists have claimed some success keeping various sharp-nosed puffers in reef aquaria, though it certainly cannot be advised for all.
Though an aquarist must significantly reduce a potential stocking list in order to include tetraodontids or diodontids, these fishes can be incredibly rewarding to care for. Indeed, puffers and porcupines alike are often prized by their owners not just as ornamental fish but as bona fide pets.