Taxonomy & naming
Pao suvattii was described by Sontirat and Soonthornsata in 1985 from specimens collected in Thailand. The Catalog of Fishes (Eschmeyer, CAS) — the authority for valid names used here — lists the combination as Pao suvattii (Sontirat & Soonthornsata, 1985), the parenthetical authority reflecting its original placement in a different genus.
Earlier literature commonly cited this species as Tetraodon suvattii, placing it in the old, near-worldwide genus Tetraodon. Subsequent revision of the Asian members of that assemblage led to the elevation of the subgenus Pao to full genus rank, and the Asian riverine puffers — including suvattii, baileyi and their relatives — now reside in Pao. Under the modern treatment, the genus Tetraodon is restricted to African species; the Asian Dichotomyctere covers the brackish-tolerant coastal puffers of that region, while Pao holds the purely freshwater Mekong-system species. This taxonomy is followed on this site and reflects current Catalog of Fishes usage.
The species epithet suvattii honours the collector or describer's associate; precise derivation is not documented in the material available.
Morphology
Like all tetraodontids, Pao suvattii has a stout, ovoid body that tapers sharply toward the caudal peduncle — a silhouette that gives it and similar Mekong puffers the "arrowhead" common name. The skin is scaleless and rough with embedded spicules rather than conventional scales, and there are no true gill covers, the gill openings reduced to a small slit ahead of the pectoral fin.
The mouth is small and terminal, armed with four fused tooth plates forming a hard beak that continuously grows throughout the fish's life and must be worn down by a diet of hard-shelled prey. The coloration in life is reported as olive to brownish green on the dorsum, fading to a pale yellow or cream underside, with a variable pattern of darker blotching or mottling. The eyes are large and mobile, capable of rotating independently — a hunting adaptation shared across the family.
FishBase data for the genus Pao place comparable species in the 2–4 in standard-length range; P. suvattii is reported by aquarist sources at roughly 2–3 in, making it a medium-small member of the genus. Precise maximum size data from peer-reviewed voucher-based measurements are sparse.
Habitat
Pao suvattii is native to freshwater streams and tributaries in northern Thailand, associated with the Mekong basin. It inhabits flowing, well-oxygenated water — the type of clean, current-influenced environment typical of upland and foothill tributaries rather than lowland floodplain lakes.
Water-chemistry data derived from comparable Mekong-basin localities and from aquarist husbandry indicate warm, soft to moderately hard conditions: temperature approximately 75–82 °F, pH in the range 6.0–7.2. The fish is strictly freshwater; there is no evidence of brackish tolerance, consistent with the broader genus Pao whose members are river specialists far inland from any tidal influence.
Wild habitat data are limited; most of what is known about the species' ecology comes from the aquarium trade rather than field surveys, so habitat descriptions should be treated as indicative rather than precisely calibrated.
Feeding
Pao suvattii is a molluscivore and durophage — a crusher of hard-shelled prey. Its natural diet in the Mekong system almost certainly centres on freshwater snails, small bivalves, and crustaceans, supplemented opportunistically with other invertebrates. This diet is the functional driver of the tetraodontid beak: the hard food wears down the continuously growing tooth plates, maintaining a functional jaw profile.
In the absence of adequate hard-shelled food, the teeth overgrow and the fish eventually cannot feed, a husbandry failure that is preventable with a well-planned diet. Aquarist sources confirm the typical puffer feeding pattern: an alert, active hunter that inspects its territory and strikes prey with precision rather than pursuing it in open water.
Mating
Pao suvattii is reported by aquarist sources as a substrate spawner in which the male is the guarding sex. Courtship involves the male pursuing and attending to a receptive female; the pair spawns over a flat surface or open bottom, and following egg deposition the female's involvement ends.
Puffers of the genus Pao do not form lasting pair bonds and are not communal; the solitary, territorial nature of the adults outside of spawning events means that any introduction of a conspecific must be managed carefully to prevent aggression. Data on wild mating behaviour are not available; what is known derives from captive breeding records in the hobbyist community.
Breeding
Captive breeding of Pao suvattii has been achieved by aquarists and follows a pattern reported for the genus: eggs are deposited on a flat substrate — a bare aquarium bottom or a flat stone — and the male guards the clutch until hatching. Incubation at 77–79 °F has been reported at approximately 5–8 days, based on hobbyist accounts. The male actively tends the eggs during this period, fanning and defending them.
The female should be separated from the male after spawning to prevent predation of the clutch and aggression. Fry care details are sparsely documented; very small live foods are expected to be required in the initial days of free-swimming. This species' guarding behaviour, if confirmed reliably across multiple records, distinguishes it from the non-guarding egg-scattering mode found in many other teleost families and places it firmly in the paternal-care category typical of Pao.
In the aquarium
Pao suvattii should be kept alone or in a carefully managed species-only setup. It is an aggressive, predatory fish with a strong territorial drive; community tanks with other species invite fin-nipping or outright predation, and conspecifics require very large quarters with clear territory breaks if they are to coexist without injury.
The continuously growing beak is the single most important dietary concern. The fish must receive a regular diet of hard-shelled live or thawed prey — freshwater snails are the preferred dental tool, supplemented with small shrimp and shellfish. Without adequate hard food the tooth plates overgrow and may eventually require trimming by an experienced aquarist or veterinarian. A diverse diet also prevents food fixation, which puffers are prone to.
Puffers are scaleless and lack true gill covers, making them acutely sensitive to certain medications; copper-based treatments must never be used, and any medication should be dosed cautiously. They are heavy eaters and produce significant waste, so robust filtration and frequent, substantial water changes are essential. When stressed or mishandled, Pao suvattii can inflate by gulping water — a defensive reflex that should not be deliberately induced, and the fish should never be lifted out of the water into air, as inflation in air causes serious harm. The skin and organs contain tetrodotoxin; handlers should wash their hands thoroughly after contact and the fish is toxic if ingested.
Conservation
Pao suvattii has not been formally assessed by the IUCN Red List and carries a status of Not Evaluated (NE). Its distribution appears centred on northern Thailand and the upper tributaries of the Mekong system — a geographically limited range that, in principle, makes it vulnerable to basin-level pressures.
The Mekong and its tributaries face significant anthropogenic stress: large mainstream and tributary dams alter hydrology and block fish movement, agricultural runoff degrades water quality in lowland reaches, and expanding human settlement increases sedimentation and habitat modification in upland streams. The extent to which these pressures specifically affect Pao suvattii populations is not documented. The species' presence in the aquarium trade — which implies ongoing collection from wild sources, at least historically — adds a further unknown variable. Formal population surveys and a Red List assessment would be of value for this and several other narrowly distributed Pao species.