Nile Puffer (Tetraodon lineatus)
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- Nile Puffer, Globe Fish, Fahaka Puffer
Additional scientific names
- Tetraodon fahaka
- These are riverine fish from Africa, obviously commonly found in the Nile originally, but have been reported in decline in that system. They tend to hunt for prey in the shallower vegetated margins of the channel, but are reported to breed in the wild at greater depths in the main channel.
- There are no external sex differences known, except that gravid (egg-laden) females develop abdominal fullness rarely seen in males.
- The fish will feed at any depth where food is available. Forward-facing and independently movable eyes give binocular vision for good depth perception to potential prey items. They will squirt water from their mouth at gravel or sand to seek partly or fully concealed invertebrates.
- Absolutely solitary in captivity other than in massive tanks when raised with conspecifics from fry stages, and even then may show aggression and territoriality after puberty up to the killing of tank mates. Best as solitary specimens.
- In the wild T. lineatus feeds largely on invertebrates (mollusks and crustaceans are the primary diet) and small vertebrates. In captivity they may be trained to non-living foods, but very high "crunch" factors are still required to wear away the four dental plates, as these modified, fused, teeth grow constantly as do those of rodents. Without wear on these incisors, they will overgrow to the point of forcing the animal into starvation. Shell-on crustaceans and smallish bivalve mollusks are their standard diet in captivity. Frozen material should be fully thawed prior to feeding to captive specimens. The fish market or grocery store is a more appropriate dietary supply place than the local pet store for these fish. Shell-on shrimp, the smaller bivalves, broken off lobster legs, etc. are excellent medium and large puffer food, just freeze in smallish batches (meal sized portions are ideal) and thaw as required i cool water. Heavy-shelled bivalves may require some breaking or crushing (with pliers for me) to give the fish the initial idea and easier access.
- Flake and pelleted foods are not recommended for puffers in general, and certainly not for large puffers such as the T. fahaka. This is not a nutritional judgement, but a technical one - these fish are adapted to, and in effect designed for, a diet of crustaceans (with shells) and mollusks (also with shells. They crush shells with their incisors, or bite chunks out of them, and then grind them up with their pharyngeal (throat) teeth. If you closely watch a puffer eating a snail, you will see bits of shell flushed out through the gills, of from the mouth. This is an evolutionary development to rid the system of much indigestible or difficult to digest material up front, as it were. Unfortunately, flake is ground as well, as are pellets, with much of the supplied food being blown out as fine powder. This is contributing to the bioload of the system without any contribution to the nutrition of the fish. Puffers, as is all too common among predators, are somewhat messy eaters at best. Magnifying their upkeep without adding as much nutrition as other food sources is not the most desirable or best practice.
- Small fish (less than 15.2cm (6") may be fed daily (I skip one day per week anyway) to the point of a lightly rounded belly. Puffers have no ribs, so food in the gut is easily seen as lumps or overall bulges, depending in part on the food density and how well it was chewed (these fish have grinding pharyngeal teeth in addition to the biting incisors for which the genus was named). A pot belly or beer-gut appearance is undesirable as some food is likely to be excreted undigested (fouling the tank unnecessarily), or may lead to gut problems (fermentation of the undigested food) with or without swimming difficulty).
- Mid-sized fish (from 15.2-30.5cm (6-12")) may be fed to approximately the same appearance on alternate days, tapering off at around a 30.5cm (12") to every third day or even less often if the specimen is not very active.
- As riverine fish from areas with large rainfall differences between seasons, they are adaptable as to water parameter by nature, from perhaps heavily silted but relatively soft floodwater up to much harder water during dry seasons of lower flow. This makes them undemanding as to water parameter of pH and TDS or hardness in captivity. But puffers in general are sensitive to very sensitive to unoxidized metabolites such as ammonia or nitrite, and do not respond well to high nitrate levels, so a cycled tank and one which is well-maintained are both needed. This is not always easy for these large (45.7cm (18")) fish which are gluttons if allowed.
- The fish are both territorial toward conspecifics and toward almost any other living thing in their territory. Whether those are seen as competition for food, enemies, or as potential food items really does not matter to the keeper. The net effect or end result is the same, injury to the other creature or death and at least partial consumption.
- These fish and most of their kin who are hunter-predators do best in a visually complex environment which affords them objects to search around for potential prey items. As visual hunters they do tend to be active diurnally, but well- or over-fed specimens will be less active. These fish, in common with other such predators (many Cichlids) in captivity quickly learn to recognize their keeper and feeding times. They do beg for food as well as any Oscar or goldfish, so sympathy over-feeding is a real possibility, and detrimental to the fish's health and longevity. Hand feeding is strongly discouraged as their incisors and strong jaw muscles are fully capable of severe injury to possible amputations. If target feeding is your practice, use tongs, forceps, or such.
- Puffers are notorious for their ability to inflate with water as a means of avoiding being preyed upon themselves. Lacking the ribs most fish have to anchor their musculature and a very flexible spine, and having a multi-pleated stomach coupled with a throat valve which can effectively seal off that stomach after it is inflate with water, they can quickly form a near-sphere with the diameter of their nose to caudal peduncle length. They also have spines in their skin which erect themselves a the highly elastic skin is stretched by inflation. The increase in visual size and perceived mass, with spines all over their bodies, serves to discourage many predators from attack. Note that all of this involves inflation with water. If removed from the water, puffers may in their fright inflate with air. Their anatomy and the presence of air in their stomach together block the release function of the stomach valve, so such fish frequently are unable to deflate and are likely to die of exhaustion. Do not remove you puffer from the water if there is any way to avoid it - use bags or buckets to catch the fish. Captive puffers, especially growing young puffers, do 'practice" inflation with water, which can be startling to their keeper if such is observed, but is over quickly and is harmless.
- Should inflation fail, wild puffers do have a final defence - they may be toxic with either of two related very potent neurotoxins. These toxins are not created by the fish, but stored by them from raw materials obtained in their diets in the wild. Wild-caught puffers (only a very few are tank bred currently, and only one commercially in the USA) do lose their stored toxins over time, but the extinction curve of such loss in unknown. Do not eat your pet puffer.
- In consequence of their peculiar body plan, puffers do not swim as do most fish by curving and flexing the body. Most slow swimming is performed by the pectoral fins, with steering and stability provided by the dorsal, anal, and caudal fins. The genus lacks pelvic fins, part of their adaptation for inflation. Their swimming is so finely controlled that puffer can rotate around an object of interest while directly facing it head-on - a very rare behaviour in fish. They can also use the caudal fin for rapid propulsion through the water. Do not be fooled by that somewhat blimp-like body; puffers, especially Fahakas and a few other relatives, can swim with surprising speed. Their peculiar anatomy also calls for rather boxy tanks to house them. They lack the lateral flexing that most fish use for routine swimming. This also requires more space for them to turn around than similarly sized fish with more standard anatomy. If the shortest dimension of the tank is less than one third of the fish's length plus that total adult length, some caudal (tail) fin damage, or mouth or nose damage may, or is likely to, occur.
- As with many fish, they do prefer a somewhat sheltered sleeping or napping spot. Do not try for a real cave - too dangerous for a fish of this size and strength. Settle for extremely well-braced wood or plants with over-hanging and semi-floating foliage such as Crinum or the larger Vallisneria species.
- Young T. lineatus commonly bury themselves in the substrate (both defensive and lurking predator behaviour), especially if sandy, but even at times in gravel. With maturity this behaviour is usually seen less often to never, but some individuals do persistently bury themselves into adulthood.
- Very small or young Fahakas show mottled blotchy colouration without strong colours and may be confused with several other freshwater family members. Juveniles develop mature colouration gradually, with some flank stripes appearing most often first for me. True adult colour may be the last to show, and is in part responsive to tank lighting and substrate colour (many fish reduce contrast between themselves and their surroundings). Fish asleep (napping or dark/tank light off phase) are very likely to revert to some degree to very immature mottled or relatively uncoloured appearance, but recover routine colouration shortly after waking. Fish which are ill or or otherwise stressed are likely to appear darker than normal.
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