Amazon Puffer Care Sheet
- Macauley Sykes
- Sep 3, 2020
- 21 min read
Updated: Sep 9
This care sheet is written with the aim of providing 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
Sphoeroides asellus (syn. Colomesus asellus), more widely known in the aquarium trade as the Amazon puffer, and sometimes marketed under regional names such as Peruvian puffer or South American puffer, is a small New-World pufferfish of striking ecological and taxonomic interest.
Native to northern South America, it inhabits some of the continent’s most important river systems, including the Amazon Basin and its vast network of tributaries, as well as portions of the Orinoco drainage and adjacent coastal river systems. Records suggest that while the species is primarily a freshwater inhabitant, it demonstrates a notable tolerance of mildly brackish and estuarine waters, a trait that aligns with the broader adaptability seen within the genus Sphoeroides.
In the wild, S. asellus is commonly encountered in shoals, often moving through open water rather than hugging structure, a behaviour somewhat atypical for puffers. Seasonal changes in river levels and hydrology strongly influence its movements, with individuals dispersing widely during annual flood pulses to exploit newly accessible feeding grounds. Their presence in both whitewater and blackwater systems also reflects a considerable physiological flexibility, though they are seldom reported from highly mineralised, clearwater tributaries.
From a conservation and ecological standpoint, the species is locally abundant and supports subsistence fisheries in parts of its range. Its relatively small adult size (usually 7–10 cm SL) and social nature have also made it a staple of the ornamental fish trade, with the majority of exports originating from Peru, particularly the Iquitos region.
Despite its popularity, S. asellus is a highly specialised fish that’s often misunderstood. Much of the online lore mixes marine/brackish puffer advice with freshwater Amazon puffer care, leading to persistent myths about diet, social behaviour, and water requirements. In this guide, we strip those away and focus on evidence-based husbandry you can actually follow.
Taxonomy
The Amazon puffer has a complicated naming history. For many years, it was placed in the small genus Colomesus, together with the coastal tidewater puffer (C. psittacus). However, two independent genetic studies published in 2023 showed that the freshwater “Colomesus” lineage is actually nested within Sphoeroides, a much larger genus of Atlantic and Pacific puffers. Keeping Colomesus separate would make Sphoeroides paraphyletic, so taxonomists merged the genera.
As a result, the currently valid name is Sphoeroides asellus (Müller & Troschel, 1849). This change has been adopted by the authoritative Eschmeyer’s Catalog of Fishes (version 15 Aug 2025), though many hobbyist websites and even some databases still list the fish under its older name Colomesus asellus. Both names refer to the same species, but Sphoeroides asellus is now the correct one.
This makes the Amazon puffer unique as the only freshwater member of Sphoeroides, a genus otherwise made up of coastal and estuarine species.
In the wild
The Amazon puffer (Sphoeroides asellus, syn. Colomesus asellus) is widespread across northern South America, occurring throughout the Amazon Basin (from Peru downstream to Brazil, including the Araguaia and Guaporé tributaries), the lower Orinoco, and the Essequibo system in Guyana. Some sources treat the Tocantins–Araguaia population as a closely related species (Sphoeroides tocantinensis), while others include it within S. asellus; both names may be encountered in the literature.
In the wild, this species favours shallow, sandy shorelines and beaches, often along current-swept margins exposed by seasonal water-level changes. During low water, it is frequently seen in large shoals, patrolling open sand flats and margins. They are also reported from floodplain lakes and open banks with little vegetation.
Field diet studies show an insect-dominated feeding ecology. In the upper-middle Tocantins, gut-content analyses found mayfly nymphs (Ephemeroptera) made up about half the diet of both juveniles and adults. Snails (Gastropoda) accounted for roughly a quarter of the adult diet, but only 6–7% for juveniles. Chironomid larvae, insect fragments, occasional fish scales, and traces of plant/algal matter formed the balance. These observations match field reports of puffers foraging across sand bars and shoreline litter for benthic insect larvae and other small invertebrates. The presence of fin fragments and scales in wild stomachs is interpreted as opportunistic feeding, rather than true pterygophagy. In natural habitats and aquaria alike, Amazon puffers may take advantage of already injured or weakened fish, but they are not specialised fin-eaters like some characids. Their natural diet is best described as insectivorous with a molluscivorous component, not as a scale- or fin-feeding strategy.
On these sandy beaches, Amazon puffers occur alongside schooling characins (Moenkhausia, Triportheus), cichlids (Geophagus spp.), catfishes (Pimelodus spp.), clupeids (Anchoviella, Ilisha), gymnotiform knifefishes (Eigenmannia), and flatfishes (Hypoclinemus). Such open-water assemblages help explain why S. asellus is naturally shoaling and why it thrives best when kept in groups of six or more in aquaria.
Conservation Status & Pressures
Unlike some of its relatives, the Amazon puffer (Sphoeroides asellus) is not currently considered threatened. It is assessed as Least Concern on the IUCN Red List, reflecting its wide distribution across the Amazon, Orinoco, and Essequibo drainages, and its presence in a variety of habitats from floodplain lakes to sandy main-river margins. There is no evidence of major population decline, and the species is not listed under CITES or other international trade controls.
That said, it does face some localised pressures. Large-scale alterations of South American rivers through hydropower development, deforestation, and mining are ongoing, and these can affect the sandy and floodplain habitats where this fish is often found.
In addition, the species is a regular export from Peru for the aquarium trade. While it is still abundant in the wild, reliance on wild-caught fish means aquarists have a role to play: sourcing from responsible exporters and supporting future captive-breeding initiatives helps keep pressure off natural populations. At present, the Amazon puffer remains a secure and widespread species, but responsible aquarium practices will help ensure it stays that way.
In the aquarium
The Amazon puffer is one of the most frequently kept freshwater puffers in the hobby, and demand continues to grow. Most of the trade is still supplied by wild-caught fish, primarily exported from Peru. Occasional hobbyist accounts of spawning exist, but reliable, commercial-scale breeding has not been achieved. This is largely because raising large, synchronised shoals is labour- and space-intensive, and fry would need to be grown out in numbers to maintain their social behaviour. Retailers sometimes list stock as “tank-raised,” but in most cases this simply means wild-caught juveniles grown on in holding facilities, not genuine captive-bred fish.
In nature, Amazon puffers are active, shoaling swimmers that patrol open sandy margins in large groups. To replicate this, aquascaping should balance open water for fast swimming with dense structure for exploration and retreat. One highly effective design is to keep the front of the aquarium open as a broad “runway”, while concentrating the denser hardscape and planting at the back.
This arrangement encourages puffers to actively swim in the foreground, where they are visible, while still providing the option to dart into cover when startled. The complexity of the back section also breaks lines of sight, reduces stress by allowing individuals to avoid one another if needed, and creates multiple channels for exploration. This interplay between open and structured zones mirrors the sandy beaches and vegetated margins they frequent in the wild.
The enrichment value of such scaping is considerable. Puffers are highly intelligent fish that thrive in dynamic environments, and they will constantly investigate new textures and spaces. Incorporating caves, crevices, overhangs, root tangles, and leaf-litter pockets gives them a stimulating environment full of opportunities to explore, hide, and forage. Even simple features such as half-buried wood, stacked stones, or dense root clusters can create a network of microhabitats that encourage natural behaviour.
Rotating small habitat elements, for example, moving a cluster of twigs or replacing one leaf pile with another, keeps the tank fresh and gives the puffers “new puzzles” to solve without dismantling the main layout.
A varied substrate adds another layer of enrichment. Fine sand, patches of small gravel, and pockets of leaves or detritus mimic natural feeding grounds and encourage puffers to dig, root, and sift for food. Providing different microhabitats within the same tank allows the shoal to spread out and interact in diverse ways, reducing tension while stimulating exploration.
Strong water movement and oxygenation are essential. A spray bar from a canister filter, mounted along one side wall and angled to disturb the surface, creates circulation while improving gas exchange. Additional powerheads can be positioned to generate flow lanes across the open section, with quieter eddies forming behind hardscape to provide resting areas. This flow pattern not only promotes good health but also mirrors the shallow, current-swept habitats they occupy in the wild.
To avoid accidents, all intakes and powerheads should be fitted with fine guards or anemone-style covers to prevent snouts and fins from being trapped. Keeping the waterline slightly lowered so that return flow breaks the surface enhances oxygenation further; aim for vigorous surface ripple rather than violent turbulence.
Lighting should be moderate to bright, ideally with some shaded zones created by overhanging wood or floating plants. In nature, these puffers forage both in open sunlit areas and around shaded margins, so providing a gradient is beneficial. Stronger lighting also helps support live plants, which not only improve water quality but also contribute to environmental complexity and visual barriers.
Behaviourally, aquarists should expect an engaging and restless species. A group will patrol the tank almost constantly, often synchronising their movements in loose shoals. At times, they may scatter to explore individually before regrouping. Feeding time is highly social, with puffers often competing in bursts of activity but rarely escalating to serious aggression if space and numbers are adequate. Individuals show clear curiosity towards aquascaping changes, often being the first to inspect any new addition.
Substrate
Amazon puffers don’t “wallow” like some other species of pufferfish, but they do rest on the bottom and forage right along it, so the floor needs to be soft and forgiving. Go with a fine, rounded sand (think sugar-fine to ~1 mm). It cushions bellies and fin edges, prevents scuffs, and lets them poke around without snagging on sharp gravel.
Fine sand also keeps the tank cleaner. Because it packs tightly, leftover food and debris sit on top instead of vanishing between stones, so you can hover a siphon above the surface and whisk it away.
Quick tips:
Choose inert sands (pool filter or aquarium silica). Skip coral/aragonite mixes because they will raise hardness and pH.
Rinse well before use; cloudiness settles fast with good flow.
Group size & shoaling
Group size really matters for this fish. Unlike most freshwater puffers, Amazon puffers live in large, loose shoals in nature and bring those instincts into our tanks. They don’t “school” in tight formation; they shoal, spreading out to forage while staying connected, bunching up occasionally, or when they feel threatened.
This species should always be kept in groups of at least 6 individuals. Bigger groups mean calmer fish, stronger feeding responses, and more confident exploring. With more eyes on the environment, each individual feels safer (better predator detection and dilution of risk), so they’re happier to nose around crevices and get on with normal foraging. In short, the more, the better.
Shoaling has underpinned this species’ survival for a very long time, and it doesn’t vanish in captivity. Repeated observation and broader research on social fishes show that properly sized groups have lower stress levels, lower metabolic load (more spare energy), faster growth, better body condition, and tend to live longer. That extra energy gets spent on healing, immunity, and development rather than on constant vigilance.
When the group is too small (or a fish is alone), you will often see stereotypical, stressy behaviours: nervy, erratic movement and persistent glass-surfing (often at their own reflection). These aren’t quirks of “puffer personality”, they’re the signs that the fish needs more company.
The differences between shoaling and schooling (what you’ll actually see)
Fish gather in two broad ways: schooling and shoaling.
Schooling is the tight, synchronised, one-body look you see in some tetras; everyone packed close, turning in unison even when nothing’s wrong.
Shoaling is looser: individuals forage independently but stay connected, keeping casual spacing and line-of-sight with the group.
Amazon puffers are shoalers, not schoolers. Day to day, they will spread out and browse, then pull tighter only when startled or uncertain. That bunching is a stress/defence response, not true schooling. It might look similar at a glance, but the difference matters: expecting “perfect formation” will set you up for the wrong tank layout and the wrong expectations.
What this means for you: run them in a real group, give them room to mingle and regroup, and judge success by calm, busy foraging with loose spacing, not by whether they march like a single unit.
The "single or group of six" recommendation
The oft-repeated guideline that puffers should be kept either singly or in groups of six or more may work reasonably well for certain species, such as the Spotted Congo puffer (Tetraodon schoutedeni), but it is totally unsuitable for the Amazon puffer. Applying that blanket rule to this species ignores its distinct natural history.
In the wild, S. asellus is not a solitary ambush predator or territorial lurker; it is a genuine shoaling fish. Field observations from Amazonian beaches and floodplains consistently show them moving in large, coordinated groups, often dozens strong, patrolling open sandy margins together. This is an ecological adaptation: shoaling allows them to forage more efficiently across broad sand flats, reduces individual predation risk, and maintains social interaction within the group.
When confined to solitary conditions in captivity, Amazon puffers exhibit clear signs of psychological stress. Isolated individuals often become nervous, skittish, or lethargic, and may stop feeding reliably. In some cases, they develop stereotypic behaviours such as obsessive glass-surfing or constant fin-nipping at tankmates, a sign of redirected social frustration. These problems are not minor inconveniences; they represent a fundamental welfare issue stemming from being denied their natural social context.
By contrast, when kept in appropriately sized groups, Amazon puffers display confident, active, and highly engaging behaviour. They patrol the tank as a loose shoal, break into smaller sub-groups to forage, and quickly resume shoaling after brief dispersal. Group living also spreads out social interactions, so no single fish becomes the constant target of attention, reducing aggression and stress.
For these reasons, the idea that Amazon puffers can be kept singly as a long-term solution is misleading and detrimental to their welfare. They are not a “sometimes shoaling”; they are a true social puffer, and must be treated as such in aquarium practice.
Tank size
Amazon puffers are relentlessly active swimmers. In the wild, they cover long stretches of shoreline in search of insect larvae and other prey. In captivity, they display the same behaviour, pacing the length of the aquarium from end to end. They will use every centimetre of space available, which makes tank size very important to this fish.
For this reason, an aquarium of at least 100 cm (39 in) in length is the minimum viable size for a starter group of six individuals, with a baseline of around 200 litres (≈53 US gallons). This allows for a clear swimming lane at the front while still providing scope for structural enrichment at the back and sides. Larger groups, or tanks with additional companions, require proportionally more space. As with many active shoaling fish, the principle of “bigger is always better” absolutely applies here. It is also worth considering how scale influences behaviour. In smaller aquaria, puffers may appear more restless or nippy simply because their natural drive to shoal and patrol cannot be fully expressed. By contrast, in larger aquaria with ample length and clear lanes, they settle into a smoother rhythm of swimming, exploring, and regrouping, which is far more reflective of their natural ecology.
In short, the Amazon puffer is not a species that can be “crammed in”; they need length, shoaling space, and enrichment. Meeting those needs transforms them from potentially frustrating fin-nippers into one of the most rewarding and watchable puffers in the hobby.
Water values
Maintain the following water parameters:
pH: 6.2–7.2
Temperature: 24–28 °C
Hardness (GH): 4–10 dGH preferred (tolerates up to ~15 dGH).
Ammonia (NH₃/NH₄⁺): 0 ppm
Nitrite (NO₂⁻): 0 ppm
Nitrate (NO₃⁻): <15 ppm (lower is better).
Why these numbers?
They track the chemistry of the whitewater/clearwater habitats this species frequents: the Amazon mainstem is near-neutral with pH ~6.6 (±0.2) and low mineralization (~45 µS/cm conductivity), while clearwater tributaries like the Tapajós/Tocantins run neutral to slightly basic, with low dissolved solids; field measurements from the Tocantins report pH ≈7.4 and dissolved oxygen typically ~6.6–7.7 mg/L. These support a slightly acidic–neutral aquarium target.
Surface temperatures in these rivers range from 24–29 °C, so the aquarium target of 24–28 °C reflects typical conditions.
Hardness is naturally low across much of the range (low conductivity), but husbandry sources and tolerance data indicate soft to moderately hard water is acceptable, with upper tolerance ~15 dGH if acclimated.
Natural nitrate in these rivers is very low (e.g., ~0.11 mg N/L in the Tocantins), so a husbandry target of <15 ppm NO₃⁻ keeps conditions far cleaner than the species’ toxicity limits and aligns with best practice for active shoalers.
Seasonal oxygen can dip in the turbid mainstem, but the current-swept, beach-margin habitats used by S. asellus favour well-oxygenated conditions, hence the emphasis on surface agitation and steady flow.
Tankmates
The Amazon puffer has a reputation for being unusually social and relatively tolerant, which has led to it being marketed as a “community puffer.” While this is only partly true, it is fair to say they are far less aggressive than many other puffer species.
Their curious, tactile foraging style does, however, mean they may nip fins opportunistically, particularly on long-finned or slow-moving tankmates.
This isn’t just anecdote: stomach contents are dominated by aquatic insects and snails, but small amounts of scales and fin tissue from other fish also occur. This shows they are not specialised fin- or scale-feeders, but opportunists that will take advantage of a slow, long-finned, or injured fish. In aquaria, that translates to occasional exploratory nips, especially if tankmates make easy targets.
In practice, Amazon puffers are best treated as the centrepiece species in a species-only aquarium, or kept with very carefully chosen companions. They thrive when maintained in groups of at least six, with larger groups (8–12 or more) being even better for spreading interactions and encouraging natural shoaling behaviour. A well-fed group in a stimulating environment is far less likely to harass other fish.
Suitable (with care):
Fast, tight schooling, short-finned characins in large numbers (12–20):
Rummy-nose tetras (Hemigrammus rhodostomus / H. bleheri)
Cardinal tetra (Paracheirodon axelrodi)
Black neon tetra (Hyphessobrycon herbertaxelrodi)
Lemon tetra (Hyphessobrycon pulchripinnis)
These species all come from Amazonian or nearby South American rivers and thrive in soft, slightly acidic to neutral water with steady flow — directly compatible with puffer requirements.
Otocinclus spp. (true Otos), but only in mature, algae-rich tanks and in their own group (6–10). Provide boltholes and monitor closely during introduction. They, too, come from oxygen-rich, current-swept habitats and fit the same water chemistry.
Unsuitable:
Long-finned or slow fish: guppies (Poecilia reticulata), angelfish (Pterophyllum spp.), gourami (Trichogaster/Trichopodus spp.), Bettas (Betta splendens), fancy livebearers.
Bottom dwellers prone to close contact: many Corydoras spp., small plecos (Hypostomus, Ancistrus, etc).
Shrimp and snails: treated as prey.
Aggressive or territorial species: risk boxing puffers into tight spaces.
Summary:
Safest option: species-only tank.
Viable with care: fast, short-finned schooling characins + Otocinclus.
Avoid: slow, long-finned, aggressive, or invertebrate tankmates.
Bottom line: Amazon puffers are not true fin- or scale-feeders, but they will take the opportunity if it presents itself. If companions don’t meet the “fast + short-finned + in numbers” rule, they’re at risk.
Buying Healthy Amazon puffers
Whenever you can, hand-pick at the store rather than buying sight-unseen. Wild-caught Amazon puffers vary a lot in condition, and turning around a badly underweight fish is hard even for experienced keepers.
At the shop: what to do
Ask the basics: how long they’ve had them, any losses, what treatments (if any) were given, and what they’re eating.
Watch them feed: a good sign is quick interest and purposeful pecking at insecty foods (e.g., bloodworm, blackworm, daphnia).
Pick a matched group: choose fish of similar size/condition so no one is outcompeted.
What to look for (green flags)
Body & weight: rounded, gently torpedo-shaped fish with a full, not pinched, belly; no sunken “temples” behind the eyes.
Behaviour: bright, curious, cruising with the group; responsive to movement but not frantic.
Breathing: steady gill movement on both sides; no gasping or flared opercula.
Fins & skin: tidy edges, no fraying, ulcers, white fluff, or red streaks.
Mouth/teeth: beak aligned and neat (not overgrown or chipped); no constant gaping.
Faeces: normal brown/green granules rather than white, stringy strands.
Red flags: Walk away if you see
Knife-edge bellies, hollow heads, or a dark, blotchy stress pattern.
Glass-surfing, head-standing, spinning, or isolation from the group.
Rapid breathing, scratching, or red threads at the vent (possible parasites).
Ragged fins or obvious wounds.
After purchase
Plan a quarantine period (ideally 4–6 weeks) with high oxygen, frequent small feeds, and close observation of weight and faeces. Many wild fish carry internal parasites; have a deworming plan ready and follow a proven protocol.
In short: choose bright, well-filled, active fish that eat on cue and look cohesive as a group. Starting with good stock makes everything that follows (shoaling, feeding, long-term health) much easier
Treating for parasites
Because virtually all Amazon puffers in the trade are wild-caught, the one treatment we recommend prophylactically is for internal parasites (endoparasites). Even “healthy-looking” fish can carry worms for weeks without obvious signs, and by the time weight loss shows, recovery is harder.
Plan to quarantine your group and deworm them early.
What to use (and why)
Levamisole HCL (e.g., eSHa NDX): first line for nematodes (roundworms) such as Capillaria, Camallanus, Contracaecum, Eustrongylides, etc. It’s very effective and well-tolerated by puffers.
Praziquantel (e.g., PraziPro): use if you suspect or want to cover cestodes (tapeworms); it also has activity against many trematodes (flukes).
Notable behaviour
Smart and people-aware. Amazon puffers are highly intelligent fish with strong powers of recognition. They quickly learn to associate their keeper with food and will gather at the glass in anticipation, often tracking your movements along the tank front. Many aquarists describe them as “begging” fish; responsive, alert, and seemingly aware of routines. This people-awareness is part of their charm and makes them one of the more engaging puffers to keep.
Busy cruisers. In a settled aquarium, Amazon puffers are rarely still. They spend much of the day patrolling the length of the tank in loose shoals, swimming end-to-end at speed, before pausing to investigate interesting features. They browse surfaces, poke at crevices, and sift through leaf-litter pockets in search of insect larvae or small invertebrates. Unlike many puffers that are ambush-oriented or territorial, S. asellus is a continuous explorer, filling the foreground with movement.
Highly social. These puffers are unusual among their family in being a true shoaling species. Groups will often synchronise their swimming, pivot and turn together, then break off briefly into sub-groups before re-forming. This social rhythm gives them a dynamic presence in the aquarium. Solitary individuals, by contrast, may become restless or withdrawn — reinforcing why they should always be kept in groups.
Curious investigators. Amazon puffers interact with their environment constantly. They will explore new hardscape, probe into caves or under branches, and repeatedly check “favourite” spots. Small scape changes, e.g adding a fresh leaf pile, a cluster of twigs, or a new hiding place, are often met with immediate inspection by the entire group. Their problem-solving nature makes them well-suited to enrichment through feeding puzzles, scattered foods, or live prey items that encourage hunting behaviour.
Playful shoaling dynamics. Within a group, mild sparring and jostling can occur (short bursts of chasing or circling), but in a properly sized shoal, this rarely escalates. Instead, it forms part of their social communication. A larger group size spreads this energy evenly, preventing any one fish from being singled out. The result is a lively but harmonious display.
Day-long activity. Amazon puffers are diurnal and remain active throughout daylight hours. They will often patrol together after feeding, then settle into quieter browsing later in the day. At night, they scatter into sheltered areas within the scape, resting among roots, behind wood, or beneath leaves before regrouping in the morning.
Sexual dimorphism
There’s no reliable external way for a home aquarist to sex Amazon puffers (Sphoeroides asellus). They lack the clear colour, fin, or body-shape differences you see in some other puffers (e.g., pea puffers). In shops and at home, both sexes look essentially the same.
Feeding
Amazon puffers are best described as insectivores. Gut-content analyses from wild populations in the upper–middle Tocantins show that nearly half of the diet is made up of mayfly nymphs (Ephemeroptera). Snails form a significant part of the diet too, roughly 25% of adult intake, though only 6–7% in juveniles, which lean more heavily on softer-bodied prey.
The remainder consists of non-biting midge larvae (Chironomidae), assorted other aquatic insects and fragments, occasional fish scales and fin tissue, and small traces of plant or algal material.
This profile confirms them as active benthic foragers, picking through sandbars, leaf litter, and shoreline debris for invertebrates.
For aquarists, the most important factor in long-term success is to provide a varied, balanced diet that mirrors this mix as closely as possible. Fortunately, Amazon puffers are greedy and adaptable once settled. Unlike some puffers, they are not especially fussy and will accept a wide range of food types; live, frozen, and even high-quality prepared diets if introduced properly. Variety is essential both for nutrition and for mental stimulation.
Our preferred foods for these fish include:
Fluval® Bug Bites™ (read below)
Repashy - Grub Pie (for fish)
Small snails
Small earthworm (wisps)
Pinhead crickets
Woodlice
Aphids
Mosquito larvae
Glassworm (phantom midge larvae)
Grindal worm
Blackworm
Bloodworm
Fish scales (read below)
Suggested breakdown (by proportion):
~40% insect-based pellets (Fluval® Bug Bites™)
~25% snails (bladder, ramshorn, small terrestrial)
~15% insects (crickets, aphids, cockroaches, woodlice)
~10% variety mix (bloodworm, glassworm, blackworm, grindal worm, whiteworm, etc.)
~5% earthworm (small chopped pieces)
~5% Repashy gel foods (Grub Pie, Soilent Green)
Foods to avoid
Do not offer krill, cockles, mussels, clams, oysters, or other large bivalves.
Avoid Malaysian trumpet snails (Melanoides tuberculata): shells are too hard, little meat, and risk of injury.
Feeding guidance
Feed 2–3 small meals daily instead of one large feed.
Scatter feed to encourage natural shoaling and foraging.
Mix textures (crunchy, soft, wriggly) for enrichment.
Remove uneaten food quickly to prevent water quality issues.
Dental challenges (and the practical fix)
Like all puffers, Amazon puffers have a continuously growing beak formed from fused teeth. In their case, growth is exceptionally fast: the beak is constantly replaced in stacked bands, and without steady abrasion, the teeth will overgrow to the point where the fish can no longer feed. In the wild, this isn’t a problem. Their diet of benthic insect larvae (mayflies, midges, and other chitinous prey) involves endless browsing on hard surfaces like wood and stones, which naturally keeps the beak worn down.
In captivity, however, this presents a major challenge.
The problem in aquaria
In captivity, puffers lack this constant supply of firm-bodied prey and hard feeding surfaces. Aquarists are often told they will need to learn sedation and trimming with cuticle clippers. While dental trimming is possible in emergencies, it is not routine care and should be regarded as a last resort. Frequent trimming is stressful, risky, and above all, a sign that the diet is not providing the necessary abrasion.
Feeding snails alone will not reliably prevent overgrowth. A single adult can consume dozens of snails per week, and scaling this up to a shoal is unmanageable for most hobbyists. Their primary wild staple (mayfly larvae) cannot be provided in realistic quantities either.
The practical solution
The most effective long-term strategy is a combination of hard insect-based pellets, supplemental snails, and scraping opportunities:
Hard insect-based pellets: Products such as Fluval® Bug Bites™ or Repashy Grub Pie should form the core diet. When they are eaten promptly before softening, they mimic the firmness of chitinous prey and provide daily wear on the beak. They are also nutritionally close to the natural insect-heavy diet.
Snails as enrichment:
Best options: bladder snails (Physella acuta), ramshorn snails (Planorbella duryi), and small/young terrestrial snails from reptile or human food cultures.
Avoid: Malaysian trumpet snails (Melanoides tuberculata), which have very hard shells, little nutritional value, and carry a risk of injury.
If culturing, maintain snail colonies in mineral-rich water to ensure proper shell hardness. Snails should be seen as an enrichment supplement, not the sole abrasive food.
Scraping opportunities: Puffers are believed to scrape algae and biofilm from stones in the wild, as observed in their close relative Sphoeroides psittacus. This behaviour can be encouraged in aquaria by preparing Repashy (e.g., Grub Pie, Soilent Green), smearing it onto smooth rocks or pieces of wood, and submerging them. Puffers will scrape-feed across these surfaces, combining nutrition with tooth wear. Offering plant-based formulas like Soilent Green also reflects the small amount of plant matter found in gut contents.
Key point: If puffers are maintained on a diet of firm insect-based pellets, with occasional snails and regular scraping opportunities, dental overgrowth is usually avoided. If trimming becomes necessary more than once in a rare emergency, it is a warning sign that diet and husbandry need to be revised.
Tips for keepers
Rotate snail feedings as enrichment, not the mainstay.
Offer several small meals per day to mimic natural browsing.
Monitor teeth regularly; slight growth is normal, but “buck-teeth” or difficulty feeding requires immediate action.
Filtration and tank maintenance
A group of Amazon puffers generates a substantial bioload. These are busy, fast-moving fish that feed often and produce waste accordingly. Their aquarium needs robust filtration with both strong biological capacity and effective mechanical polishing.
For most keepers, a large canister filter is the simplest option. A spray bar positioned along one side helps maintain circulation and oxygenation, which is critical since puffers naturally inhabit well-aerated, flowing margins. In larger systems, a sump can be an excellent choice. A properly designed sump offers high media volume, stable water chemistry, excellent gas exchange, and flexibility for equipment placement (heaters, CO₂ reactors, refugia, etc.), keeping the display tank uncluttered.
However, even the best filters won’t make up for poor maintenance.
Clean, stable water is non-negotiable:
Keep nitrates under 15 ppm, ideally closer to zero.
As a working rhythm, change at least half the water weekly. Many aquarists prefer more frequent partial changes, especially in heavily stocked tanks or when feeding heavily.
Watch for detritus accumulating in complex scapes. The roots, branches, and leaf litter that enrich a puffer tank also trap waste. Siphon gently around these areas to prevent hidden build-up.
Why Keep Nitrates Low?
Amazon puffers are highly sensitive to long-term deterioration in water quality. Chronic nitrate exposure in freshwater fishes is linked to:
Suppressed immunity, increasing susceptibility to parasites and bacterial infections.
Reduced growth and feed efficiency, especially problematic for a shoaling species with a high activity level.
Shortened lifespan and impaired reproduction over time.
For Amazon puffers, water quality is not just about survival, it is about enabling them to thrive. With consistently low nitrate, they reward keepers with bright colours, strong group dynamics, and vigorous daily activity.
Inflation
Amazon puffers can inflate themselves when frightened or stressed.
They should never be provoked into inflating!
If the fish needs to be moved for whatever reason, it should be herded into a watertight container under the surface of the water to prevent it from inhaling air.
Toxicity & Toxin Origin
Amazon puffers (Sphoeroides asellus, syn. Colomesus asellus) do not follow the usual pufferfish pattern of carrying tetrodotoxin (TTX). Instead, scientific studies have shown that they can accumulate paralytic shellfish toxins (PSPs) such as saxitoxin (STX) and gonyautoxins (GTX-2, GTX-3). These toxins are not produced by the fish themselves but are acquired indirectly through the food chain, likely from algae, bacteria, or invertebrates in their natural diet.
For aquarists, the key point is that Amazon puffers are not dangerous to keep in the home aquarium. The toxins are concentrated internally and present a risk only if the fish is eaten. Normal handling, tank maintenance, or accidental contact carries no hazard.
Disclaimer
Pufferfish health information given on this site is not intended to act as or replace the advice of a certified veterinary professional. If your pufferfish is experiencing a medical emergency, contact an experienced aquatic veterinarian immediately.
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The main priority at Pufferfish Enthusiasts Worldwide will always be to provide the most accurate and up-to-date information pertaining to individual species of pufferfish and their care. Although we do greatly encourage the use of binomial names (scientific names), because common names can be so misleading for pufferfish, we sometimes have to make concessions with the care sheets for SEO reasons. We realise that most people are not going to search "Sphoeroides asellus care" and are instead more likely to search for "Amazon puffer care", so this care sheet is going to refer to them by their most frequently used common name so that new and prospective owners will be able to find this information through a Google search.
