Pao Suvattii Pufferfish Care Sheet
- Macauley Sykes
- Apr 9, 2020
- 22 min read
Updated: Oct 20
This care sheet is written with the aim of providing the 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 Pao suvattii is one of the Mekong’s most formidable and enigmatic freshwater puffers, a species that captures both the quiet patience and sudden violence of life on the riverbed. Endemic to the lower Mekong basin, it inhabits Thailand, Laos, and Cambodia, where the great river slows and deepens into silty channels, flooded forests, and backwater pools rich in fine sediment.
Here, half-buried beneath the sand, P. suvattii waits in stillness until movement above betrays its prey. In a flash of precision and power, it erupts from concealment, a master ambush predator shaped by the pulse of the river itself.
First described by Sontirat in 1989, the species was long known under the genera Tetraodon and Monotrete until the landmark revision by Kottelat in 2013 redefined the Southeast Asian freshwater puffers as members of the genus Pao. This reassignment reflected growing recognition of their distinct evolutionary lineage within the family Tetraodontidae, a group adapted not to coral reefs or coastal estuaries, but to the complex inland waters of Asia’s great rivers.
Reaching around 12–15 cm (4.7–6 inches) in length, it is compact but muscular, with a flattened profile, broad snout, and cryptic patterning that blends perfectly with its surroundings. In captivity, lifespans of ten to twenty years are not unusual when water quality, diet, and environmental enrichment are maintained to a high standard.
Known variously as the Mekong Puffer, Pignosed Puffer, Hognosed Puffer, and Arrowhead Puffer, these names reflect the fish’s distinctive appearance and structure. The upturned snout and broad, flattened head give it a pig-like profile, inspiring the “Pignosed” and “Hognosed” names, while the term “Arrowhead” refers to the dark triangular pattern often visible across the crown of the head.
In the Wild
Pao suvattii is native to the lower Mekong Basin, where it occurs across Thailand, Laos, and Cambodia. Verified records place it within the main Mekong channel and major tributaries such as the Sekong, with a 2024 study confirming its presence in Siem Pang Wildlife Sanctuary, northeast Cambodia. Within this system, P. suvattii occupies deeper river sections, silty margins, and floodplain channels that retain steady current and oxygenation.
Field observations describe its habitats as slow to moderately flowing stretches of large rivers, often in deep pools or side channels where fine sand and silt accumulate. The Cambodian specimen was collected from a pool roughly 20 m × 30 m × 3 m, with clear, dark water and gentle movement over a rocky base surrounded by flooded forest. Such environments provide both stability and cover, allowing P. suvattii to bury itself within the substrate while maintaining access to well-oxygenated water and a steady drift of prey.
In these habitats the fish spends much of its time pressed against or buried within the substrate, emerging to feed on passing crustaceans, worms, and small fishes. Its muscular body and flattened head are perfectly adapted for anchoring against moderate current while remaining hidden, an approach suited to river pools where flow is constant but not turbulent. The species’ reliance on soft sediment for concealment restricts it to areas where the current is gentle enough to allow sand to settle, yet strong enough to prevent stagnation.
Hydrological studies from the lower Mekong show these reaches to be well-oxygenated, with flow that fluctuates seasonally as floodwaters expand and retreat. During the wet season, increased discharge rejuvenates these habitats with fine sediment and oxygen-rich water, while in the dry months, pools become calmer and more stable. Across these conditions, P. suvattii remains a constant presence along the benthos, shifting little except to ambush prey or adjust position with changing depth.
Typical field conditions recorded from comparable sites within the lower Mekong basin are as follows:
pH: 6.5–7.8 (most sites near neutral)
Temperature: 24–30 °C, varying with season and depth
Conductivity: generally 100–400 µS/cm
Dissolved Oxygen: consistently high, often above 6 mg/L in the main channel, remaining moderate in deeper pools
These parameters describe the dynamic but balanced character of P. suvattii’s environment: well-oxygenated, mineral-moderate, and rich in fine sediment. It is an ecosystem built on movement without chaos, where sand and water shift in rhythm rather than force. Within this setting, P. suvattii lies in wait, a living reflection of the river’s stillness between surges.
Diet in the Wild
There are no formal gut-content or isotope studies for Pao suvattii, so its feeding ecology must be inferred from habitat records, co-occurring fauna, and functional morphology. Field sources place the species on or in the substrate of large Mekong rivers, where it occupies deep pools and side channels with fine sediments or rocky beds. A 2024 record from Siem Pang Wildlife Sanctuary in northeast Cambodia documents a specimen from a small, deep pool with slightly flowing, clear-dark water over rock, consistent with slow to moderate flow in riverine refugia.
Within these habitats, likely prey include benthic and near-bottom organisms that share the same margins and pools. Plausible candidates are freshwater prawns of the genus Macrobrachium, juvenile gecarcinucid crabs such as Esanthelphusa spp., and small or juvenile fishes that rest or forage at the substrate, including gobies like Glossogobius giuris and floodplain cyprinids such as Henicorhynchus and related genera. Worms and insect larvae are also abundant in the same sediments and fall within the strike envelope of a buried ambush predator. These taxa are documented as widespread in the lower Mekong and are presented here as co-occurring prey candidates rather than confirmed stomach contents.
The species’ morphology supports this interpretation. Its upturned snout, fused dental plates, and heavily muscled jaws are built for crushing and suction, not pursuit. P. suvattii buries itself beneath the substrate, leaving only its eyes exposed, and waits motionless until vibration or shadow signals the approach of prey. With a rapid contraction of the body and sudden expansion of the buccal cavity, it creates a powerful vacuum that draws prey into its mouth. This ambush suction mechanism allows it to capture crustaceans and bottom-dwelling fish within a narrow strike radius. The combination of strike mechanics and crushing dentition points to a diet dominated by crustaceans and hard-bodied invertebrates, supplemented by small fish that drift or forage close to the bottom.
Toxicological evidence provides independent corroboration of this benthic linkage. Unlike many marine puffers that retain tetrodotoxin, P. suvattii selectively accumulates saxitoxins, with studies reporting retention in ovary and skin. In freshwater systems these toxins originate with cyanobacteria and move through grazers and detritivores to crustaceans and small fish, aligning with a diet focused on benthic invertebrates and near-bottom fishes. The toxin data identify the pathway rather than specific prey items, so they are best viewed as contextual support.
Seasonal dynamics of the lower Mekong further shape prey availability. Flood pulses expand habitat and boost invertebrate production in margins and floodplains. Dry-season contraction concentrates fishes and invertebrates in deeper pools. These hydrological cycles are well documented for the basin and provide a reasonable backdrop for interpreting how an ambush predator at the substrate would encounter prey through the year.
Taken together, this evidence depicts a predator evolved for precision and patience. Pao suvattii feeds on the life that inhabits the sediment, the crustaceans, worms, molluscs, and small fish that crawl, dig, or drift across the riverbed. Its diet is a reflection of its anatomy and its world, slow, deliberate, and perfectly attuned to the rhythm of the Mekong.
Conservation Status
The IUCN Red List currently classifies Pao suvattii as a species of Least Concern, based on an assessment published in 2011. At that time, populations were considered stable across the lower Mekong Basin, and no specific threats were recorded as causing a measurable decline. Since then, however, the river has undergone significant transformation.
Across the basin, hydropower construction, damming, sand extraction, and floodplain modification have altered flow regimes and sediment distribution. The deep, slow to moderately flowing pools and side channels that P. suvattii inhabits depend on balanced sediment renewal and stable oxygen levels. As these dynamics shift, the silty substrates and calm margins on which this species relies are gradually being disrupted or lost.
The species remains locally present in undisturbed areas of the Mekong and its tributaries, but the long-term security of its habitat is uncertain. The quiet backwaters and depositional zones that define its ecological niche are among those most vulnerable to hydrological alteration and pollution.
Until the IUCN reassesses P. suvattii under modern conditions, its official status will remain “Least Concern,” yet its real-world outlook is increasingly tied to the health of the Mekong itself. Protecting sediment balance, water quality, and the flood pulse that sustains these habitats will be vital if this remarkable ambush predator is to endure in the years ahead.
In the Aquarium
Most Pao suvattii entering the aquarium trade are wild caught, collected from the sandy and silty channels of the lower Mekong Basin. Despite this, they adapt remarkably well to captivity when housed in an aquarium that reflects the calm, structured complexity of their natural habitat. Success with this species depends not on decoration, but on design: a tank that offers security, shade, and function above all else.
The aquarium should feel secure and enclosed, built to provide shelter and vantage points rather than open swimming space. P. suvattii is naturally cautious, but when it feels protected, it quickly becomes confident and active, exploring the aquarium and watching movement beyond the glass. A carefully arranged scape allows it to display its natural behaviours: wallowing, ambushing, and slow, deliberate patrols.
Begin with a soft sand substrate deep enough for wallowing, as this forms the foundation of the environment.
Build the main structure at the back of the aquarium, using smoothed boulders, driftwood, and interlocking rockwork to create stable, shaded formations.
These could form recesses, arches, and root-like tangles where the fish can rest and observe unseen.
Leaving the front of the aquarium open provides both a clear feeding area and a natural stage for the puffer’s behaviour. As P. suvattii settles, it will begin to use this open ground more frequently, moving between wallowing spots and its chosen ambush sites with calm assurance.
Plants are optional but beneficial for softening the layout and offering additional cover. Hardy epiphytes such as Anubias and Microsorum pteropus (Java fern) attach well to wood or stone and tolerate subdued light and gentle flow. Avoid rooted plants, as the puffer’s digging will quickly dislodge them.
Lighting should be soft and indirect. P. suvattii inhabits shaded, often turbid waters where bright illumination is rare. Gentle, ambient lighting helps to reduce stress and encourage natural activity.
Water flow should be moderate. A steady, directional current that moves waste toward the filter while leaving calm zones near the substrate works best. Avoid harsh turbulence, which can unsettle the fish or disturb the sand bed.
This species produces a heavy biological load relative to its size, so strong filtration and disciplined maintenance are essential. A large external canister or sump system is ideal for maintaining water clarity, biological stability, and oxygenation. Regular large water changes are vital to prevent nitrate accumulation. P. suvattii thrives in clean, well-oxygenated water with stable parameters and minimal dissolved waste.
With a well-structured tank and stable conditions, Pao suvattii soon becomes a confident and engaging fish. It settles quickly, uses its environment with purpose, and displays the patient precision that makes it one of the most rewarding ambush predators to observe in freshwater aquaria.
Substrate
In the wild, Pao suvattii spends much of its life buried in sand or fine silt, lying in wait for passing prey. It is a true ambush predator that relies on concealment and stillness rather than movement or pursuit. In the aquarium this behaviour remains identical. A relaxed specimen will often settle flat against the bottom, covering itself with sand until only the eyes are visible. Fine sand is not optional. It is essential.
This species must be given a soft substrate that allows it to wallow naturally without risk of abrasion. A smooth, fine sand replicates the texture of the Mekong riverbed and enables the fish to rest and hunt in complete comfort. Without it, P. suvattii becomes stressed, restless, and unable to display normal behaviour.
Recommended substrate details:
Ideal choice: fine, sugar-soft sand
Grain size: 0.2–0.5 mm (very fine and smooth)
Best types: aquarium-grade fine sand, well-rinsed play sand, or smooth pool-filter sand that is chemically inert and free from sharp grains
Avoid: gravel, coarse sand, or any plant soils and decorative substrates that contain rough or angular particles. Even rounded gravel prevents proper wallowing and can injure the fish when it tries to bury itself.
To maintain the sand correctly, aim for a natural bed that supports good circulation and prevents compaction:
Keep the sand bed around 2–5 cm deep in most areas, adding a little more in the puffer’s favourite wallowing sites
Stir or rake small sections during weekly water changes to release trapped gases and maintain oxygen exchange
Maintain strong surface flow so debris does not settle and collect in dead spots
When siphoning, vacuum lightly across the top rather than disturbing the lower layers
A soft sand substrate is not decorative but fundamental to the species’ welfare. It defines how the fish behaves and how it experiences its environment. When given the right substrate, Pao suvattii settles quickly, displays calm, deliberate movements, and spends long periods resting half-buried in the open. It is in this natural posture that the fish reveals its true character: composed, patient, and completely at home.
Tank Size
In nature, Pao suvattii spends most of its life resting along the riverbed, buried in sand or settled beside driftwood and stones. It moves only when necessary, relying on stealth and timing rather than speed. In captivity this behaviour remains unchanged. The fish prefers to occupy a defined patch of ground and observe rather than explore, yet it still requires enough space to feel secure and to maintain good water stability.
An aquarium measuring at least 80 cm in length and 35–40 cm from front to back, with a height of around 40 cm, provides a suitable minimum footprint for a single adult.
This equates to roughly 110–120 litres of water volume, enough to establish a stable, well-filtered system and to include sand, structure, and areas of open space for the fish to settle.
Within a tank of this size, P. suvattii can display its natural behaviours, shifting slowly between hollows, burying in the substrate, and lying in ambush without feeling confined.
Larger aquariums are strongly recommended where space allows.
When provided with adequate room and structure, Pao suvattii becomes calm, confident, and visibly more interactive. It will rest in partial view, follow movements outside the tank, and occasionally reposition itself to watch from new vantage points. Cramped or featureless tanks, by contrast, often result in nervous or withdrawn behaviour. Space, security, and consistency form the foundation of this species’ wellbeing in captivity.
Water values
Maintain the following water parameters:
pH: 6.5–7.5
Temperature: 24–28 °C (75–82 °F)
Ammonia (NH₃/NH₄⁺): 0 ppm
Nitrite (NO₂⁻): 0 ppm
Nitrate (NO₃⁻): below 15 ppm (ideal)
General Hardness (GH): 4–10 °dGH
Why these Numbers?
These recommendations reflect the conditions recorded across the lower Mekong Basin, where Pao suvattii inhabits deep, slow to moderately flowing pools and side channels. Surveys of these habitats describe clear, well-oxygenated water with fine sediment or sandy substrate, soft to moderately hard mineral content, and a near-neutral pH that remains stable throughout most of the year. Conductivity readings from comparable sites typically fall between 100 and 300 µS/cm, equating to roughly 4–10 °dGH.
A pH between 6.5 and 7.5 mirrors the slightly acidic to neutral character of the Mekong’s deeper channels. These waters carry a mix of organic input from leaf litter and mineral buffering from the basin’s sediment load, which together maintain a steady chemical balance. Mid-range values around 7.0 provide the most predictable behaviour and stable appetite.
Temperature in these reaches of the Mekong commonly ranges from 24 to 30 °C, depending on depth and season. The recommended aquarium range of 24–28 °C sits comfortably within this band and reflects the stable temperatures found in deeper pools. Within this range, P. suvattii maintains balanced metabolism, consistent feeding behaviour, and good oxygen uptake. Prolonged exposure above 29 °C can reduce oxygen saturation and cause the fish to become sluggish or reclusive.
Ammonia and nitrite must always remain at 0 ppm. Like all freshwater puffers, P. suvattii is highly sensitive to nitrogenous waste. Even trace amounts cause gill irritation, laboured breathing, and loss of appetite.
Nitrate should be kept low, ideally below 15 ppm. In the wild, the constant movement of river water prevents the accumulation of organic waste. In aquaria, maintaining low nitrate levels is a measure of system health rather than toxicity. Consistently low values reflect good filtration, adequate flow, and regular maintenance.
General hardness of 4–10 °dGH and carbonate hardness of 2–6 °dKH replicate the moderate mineralisation of its habitat. This balance supports healthy osmoregulation while preventing pH instability. Water that is extremely soft can become chemically unstable, while excessive hardness tends to dull colour and irritate the skin.
While P. suvattii tolerates moderate mineral variation, it performs best in clean, stable water with steady oxygenation and minimal organic load. Flow should be gentle and continuous, enough to keep the surface lightly agitated and prevent stagnation, but never so strong that it disturbs the substrate. High oxygen levels and chemical stability are more important to this species than precision in any single parameter.
Tankmates
Pao suvattii is not a community fish.In the wild it lives alone, occupying a defined patch of riverbed that it defends with absolute certainty. It relies on stealth, territorial awareness, and the instinct to strike first at anything that enters its space. This same behaviour continues in captivity.
For this reason, P. suvattii must be kept as a solitary specimen. It should never be housed with other fish, regardless of size, speed, or species. Tank mates are either perceived as prey or as intruders and will be attacked without warning. Even fish that appear to coexist peacefully are at risk, as P. suvattii often waits until an opportunity presents itself before striking.
Pairing or group attempts invariably fail. Males and females show no long-term tolerance for one another outside of controlled breeding trials, and juveniles that seem passive when small quickly become aggressive as they mature.
Keeping P. suvattii alone is not a limitation; it is the correct expression of its natural lifestyle. A single fish in a well-structured aquarium is calm, confident, and highly interactive with its keeper. When left undisturbed, it will display the full range of its natural behaviours - resting, observing, ambushing, and exploring - without the stress or conflict that companions inevitably cause.
A solitary setup is therefore the only appropriate way to maintain this species. It ensures safety, stability, and the behavioural authenticity that makes Pao suvattii such a fascinating and rewarding fish to keep.
Sexual Dimorphism
Sexual dimorphism in Pao suvattii is minimal and unreliable for visual sexing. No consistent external traits have been identified that allow males and females to be distinguished with confidence.
Some aquarists have reported that males appear slimmer and slightly more angular in head shape, while females develop a deeper body and broader abdomen, especially when gravid. However, these differences overlap heavily with feeding state, age, and general condition, and cannot be used as dependable indicators of sex.
At present, the only reliable methods of sex determination are direct observation of spawning in a known pair or internal examination. For practical husbandry, P. suvattii should therefore be regarded as unsexable by external features.
Notable behaviour
Pao suvattii is a true ambush predator. In the wild it lies buried in sand or pressed against submerged structure, remaining motionless for long periods until movement enters its strike zone. The same behaviour occurs in captivity, where long stillness is followed by a sudden, explosive strike.
This species has a powerful feeding reflex and will attack anything that moves within range of its head. Aquarists must exercise caution during maintenance. There are many confirmed reports of keepers being bitten while cleaning or moving objects in the tank. These bites can easily break the skin. Always use tools rather than bare hands when working inside the aquarium.
Wild-caught specimens sometimes inflate or posture at their own reflection as they settle into captivity. This behaviour is usually temporary. Once the fish recognises the reflection as harmless, it stops displaying and resumes normal behaviour.
When confronted by what it perceives as a rival, P. suvattii performs a distinct threat display.
It begins by fixing its gaze on the intruder, holding position with an intense forward stare. If this fails to deter the perceived challenger, the fish lowers its head and moves forward slowly in a deliberate, warning motion. It may then open its mouth to expose the teeth while circling the other fish. If the situation escalates further, it inflates its body and swims with sharp, erratic movements intended to intimidate. The final stage is a direct charge, intended to bite and drive the threat away.
If a specimen is seen challenging its own reflection, reduce the lighting and allow it to calm. Reflections are strongest under bright light and on clear glass, so soft, ambient lighting and a darker background help prevent recurring displays.
A settled P. suvattii spends much of its time resting half-buried in the substrate, with eyes exposed and head slightly raised. It observes its surroundings closely, tracking movement outside the glass and responding to its keeper’s presence. It is solitary and territorial by nature, forming a clear mental boundary around its chosen area and reacting instantly to intrusion.
In a calm, stable aquarium with appropriate structure, Pao suvattii displays deliberate, purposeful movement. Every action, whether concealment, observation, or strike, is precise and controlled.
Feeding
Feeding Pao suvattii correctly begins with understanding what kind of predator it truly is. In the wild, this fish spends much of its time buried in sand or silt, lying motionless until vibration or shadow signals movement nearby. When the moment comes, it lunges forward in a single, explosive strike, drawing its prey in through powerful suction. The strike is short, precise, and backed by exceptional jaw strength: a design perfectly suited to capturing crustaceans, worms, and other benthic animals rather than pursuing fast-moving fish.
Field data from the lower Mekong and Chao Phraya systems show P. suvattii sharing its habitat with abundant freshwater crabs (Esanthelphusa, Parathelphusa), shrimps (Macrobrachium, Caridina), benthic snails, insect larvae, and small bottom-dwelling fishes such as loaches and gobies. These prey types, together with the fish’s heavily muscled jaws and broad, upturned snout, make it clear that P. suvattii is a crustacean and invertebrate specialist that takes small fish opportunistically. It is a facultative piscivore, not a true one.
In captivity, the goal is to replicate that diversity and nutritional balance as closely as possible. A diet built primarily around clean, gut-loaded invertebrates, supported by occasional thiaminase-free fish, provides the right mix of protein, micronutrients, and feeding stimulation while maintaining excellent water quality.
Recommended Foods
Gut-loaded earthworms
Gut-loaded cockroaches, crickets, locusts, and woodlice
Thiaminase-free fish meat, cut into manageable pieces (see Feeding Fish)
Freshwater crabs and crayfish (either whole or in chunks)
Repashy “Grub Pie” or other high-quality insect-based gel diets
Marine-derived foods such as prawns, mussels, and clams should not be used as staples. They differ nutritionally from the freshwater prey this species has evolved to digest and are often high in thiaminase, which can cause long-term deficiency.
Because this species is sedentary and digests food slowly, it does not require daily feeding. Offering food two to three times per week is sufficient for healthy maintenance and stable behaviour. Overfeeding rapidly affects water quality and can lead to internal fat accumulation.
Suggested Feeding Breakdown
The following proportions reflect the natural balance and long-term observation in captivity:
40% Freshwater crustaceans (crab and crayfish)
30% Worms and insect larvae
25% Thiaminase-free fish
5% Enrichment foods
These ratios provide a practical framework for feeding while ensuring that hard-shelled prey are offered regularly for dental maintenance and that soft foods form a varied and digestible staple.
Feeding fish
Pieces of fish can be offered occasionally to add variety to the diet of Pao suvattii, but they should never become a major food source. In the wild, this species feeds mainly on crustaceans, worms, snails, and other bottom-dwelling invertebrates. Small fish may be taken opportunistically, but they do not represent a significant part of its natural diet. The goal in captivity is to preserve that same balance.
When offering fish, always select thiaminase-free species. Thiaminase breaks down vitamin B₁ (thiamine), and long-term exposure can lead to neurological problems, appetite loss, and general decline in condition.
Recommended Thiaminase-Free Species
Tilapia (Oreochromis spp.)
Trout (Oncorhynchus mykiss)
Cod (Gadus morhua)
Pollock (Pollachius spp.)
Haddock (Melanogrammus aeglefinus)
Catfish (Ictalurus or Pangasius)
Pike or Perch (freshwater-sourced and parasite-free)
Fish to Avoid
Avoid goldfish, minnows, anchovies, sardines, herrings, and most smelts. These are thiaminase-positive and unsuitable for long-term feeding.
Preparation
Most market fish are too large to feed whole. Prepare small, clean pieces as follows:
Remove the head, fins, and internal organs
Fillet the fish, leaving scales and skin intact
Cut into manageable pieces that the puffer can swallow easily
Freeze for at least seven days to eliminate parasites
Thaw gently in cool water before feeding
Offer fish flesh no more than once every one to two weeks, alternating with the invertebrate-based foods that form the bulk of the diet. Always feed by tong to control portion size and prevent uneaten food from spoiling the substrate.
Because P. suvattii digests soft protein slowly, large or frequent servings of fish can lead to poor water quality and internal fat accumulation. Used sparingly and prepared correctly, small pieces of clean, lean fish provide useful variety without disrupting digestion or behaviour.
Feeder fish
Using live feeder fish might seem like a simple solution when a new Pao suvattii refuses food, but it almost always creates more problems than it solves.
Feeder fish, especially those from pet stores, are one of the most common sources for introducing diseases and parasites into a predatory fish's aquarium. They are often raised in crowded, unsanitary conditions and frequently carry parasites such as Ichthyophthirius multifiliis (Ich), Trichodina, Gyrodactylus, Dactylogyrus, and Camallanus worms, as well as bacterial infections like Flavobacterium columnare (Columnaris). A single introduction can undo months of careful quarantining and stable water quality.
Nutritionally, common feeder species such as goldfish and minnows are poor choices. They are high in fat, contain the enzyme thiaminase, and lack the balanced nutrition required for long-term health. Regular feeding can cause vitamin B₁ deficiency, liver damage, and digestive issues in carnivorous puffers.
Behaviourally, live feeders can also create lasting problems. P. suvattii can become fixated on movement and refuse to accept dead or prepared foods, often leading to long fasting periods, loss of condition, and nutritional deficiences.
A far safer and more effective approach is to use clean, prepared foods from the beginning. Thiaminase-free fish fillets, small pieces of freshwater prawn or crab, gut-loaded snails, and worms provide excellent nutrition while supporting natural feeding behaviour.
Once tong training is established, most Pao suvattii feed confidently on non-living foods. Live feeder fish add nothing of value to their care. They are unnecessary, unpredictable, and almost always more harmful than helpful.
Tong Training
Tong training is a highly beneficial routine for Pao suvattii. It does far more than make feeding easier. Each session helps build familiarity and trust between fish and keeper, turning mealtime into a calm, shared routine rather than a chase. Over time, the suvattii begins to recognise the tongs as a feeding signal and will readily await its meal.
Tong training offers further advantages beyond bonding. It provides more precise control over portion size, allows new food types to be introduced gradually for balanced nutrition, prevents food from scattering into the tank, and reduces overall organic waste in the aquarium.
Filtration and Tank Maintenance
Although Pao suvattii is a largely sedentary fish, it produces a considerable amount of waste for its size. Its feeding style and habit of moving through the substrate release fine debris into the water column. In a closed system, this accumulation can quickly degrade water quality long before the tank appears dirty. Strong biological filtration and disciplined maintenance are essential.
A large external canister filter is recommended for most setups. Its high biological capacity and efficient mechanical stages help maintain clarity and stability between water changes. For larger aquariums, a sump system offers additional reliability by increasing total water volume, improving gas exchange, and concealing heaters and equipment away from the display.
No filter can compensate for poor maintenance.
P. suvattii is a messy eater, often scattering fragments of food that sink and decay. These must be removed regularly. Vacuum the substrate surface at every water change, paying particular attention to the areas beneath and around stones, wood, and other hardscape where detritus tends to collect.
Clean, stable water is the foundation of success:
Keep nitrate below 15 ppm, as close to 0 as practical
Change at least 50% of the water weekly, increasing frequency after heavy feeding or during warmer conditions
Lightly vacuum the sand surface during each change to prevent compaction and waste accumulation
Maintain steady surface agitation to sustain oxygen levels and ensure good circulation
A mature biological filter combined with consistent upkeep replicates the clarity and renewal of the fish’s natural habitat. In such conditions, Pao suvattii remains calm, alert, and displays the measured, deliberate behaviour that defines this species when kept correctly.
Why Keep Nitrates Low?
Nitrate is the final product of the nitrogen cycle and, while far less toxic than ammonia or nitrite, it is not harmless. In the slow-moving, well-oxygenated waters of the Mekong Basin, nitrate levels are extremely low, often below 5 ppm. Pao suvattii has evolved in this clean, continuously refreshed environment and is not adapted to chronic nitrate exposure.
In captivity, nitrate accumulates through feeding and waste breakdown. Elevated levels create a persistent background stress that is easy to overlook but gradually undermines health over time.
Persistent nitrate exposure in freshwater fish has been associated with:
Depressed immune function, leading to increased vulnerability to bacterial and parasitic infections
Reduced appetite and slower growth, often accompanied by duller colouration
Organ strain and shortened lifespan, particularly in sedentary benthic species
Irritation to the skin and eyes in fish that rest on or within the substrate
Because P. suvattii spends much of its time in contact with the substrate, it is directly exposed to areas where waste settles and decomposition occurs. Maintaining nitrate below 15 ppm, and ideally close to single digits, best reflects the conditions of its natural river system and supports long-term health.
Achieving this requires disciplined feeding, strong biological filtration, and large weekly water changes. Consistent low nitrate is one of the clearest indicators of good aquarium management and environmental stability.
Inflation
Like all pufferfish, Pao suvattii can inflate its body by rapidly drawing water into its stomach, expanding to nearly twice its normal diameter. This defensive response makes the fish appear larger and more difficult for a predator to swallow. In nature it occurs only when the fish feels cornered or physically restrained.
In captivity, inflation is uncommon once the fish has settled. It may occur if the puffer is startled, confined, or handled, and occasionally when newly imported specimens are introduced to an aquarium. Some individuals also inflate briefly during threat displays, particularly when confronting reflections or perceived intruders.
It is also normal for P. suvattii to inflate occasionally without any clear trigger, a behaviour sometimes described as “practice puffing.” These short, controlled inflations appear to help the fish maintain muscular control of the inflation mechanism. They are voluntary, calm, and typically occur when the fish is resting or adjusting its position.
Inflation should never be provoked intentionally. Forcing the behaviour by netting, chasing, or lifting the fish from the water can cause severe stress or internal injury. If inflation occurs naturally, the fish should be left undisturbed until it deflates on its own.
When kept in a calm, stable environment, Pao suvattii rarely inflates for defensive reasons. A relaxed specimen will spend most of its time resting quietly on or within the substrate, showing no sign of distress or threat posture.
Toxicity and Toxin Origin
Pao suvattii is known to be a toxic species. Analyses of wild-caught specimens from Thailand and Laos have confirmed the presence of saxitoxins (STX) rather than tetrodotoxin (TTX), the compound more familiar from marine pufferfish. These findings place it within the group of Southeast Asian freshwater puffers that derive their toxicity from freshwater cyanobacterial and dinoflagellate food webs rather than from marine sources.
In field and laboratory studies, saxitoxin was detected in the skin, liver, and gonads, with lower concentrations in muscle tissue. The distribution pattern and potency are consistent with other Pao species tested from the Mekong Basin. The toxin does not originate within the fish itself but accumulates through the diet, passing upward through snails, crustaceans, and other benthic invertebrates that feed on toxin-producing cyanobacteria.
In captivity, this toxicity gradually declines or disappears entirely as the fish’s diet shifts away from natural prey. Specimens maintained long-term on clean, captive-prepared foods are unlikely to retain harmful levels of saxitoxin, although trace residues may persist for some time after import. For this reason, wild-caught individuals should still be handled with basic care, and their internal organs should never be consumed or fed to other animals.
There is no evidence that the toxin poses a risk to aquarists through normal aquarium contact. It is not absorbed through intact skin, nor is it released into the water in measurable quantities. However, gloves and common-sense hygiene are advised when handling deceased specimens or performing post-mortem examinations.
The presence of saxitoxin in Pao suvattii offers a valuable ecological insight rather than a practical hazard. It reflects the fish’s place within a complex freshwater food web, where microbial processes and benthic feeding link together through each level of the ecosystem.
Disclaimer
The health and husbandry information provided in this guide is intended for educational purposes only. It should not be taken as, or replace, the advice of a qualified aquatic veterinarian.
If your pufferfish shows signs of illness or is experiencing a medical emergency, seek assistance from an experienced aquatic veterinary professional without delay.
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