Green Spotted Pufferfish Care Sheet
- Pufferfish Enthusiasts Worldwide
- 5 days ago
- 15 min read
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
Dichotomyctere nigroviridis is one of the pufferfishes from the genus Dichotomyctere, best known to aquarists as the Green Spotted Puffer (commonly abbreviated GSP).
This species was formerly placed in the genus Tetraodon, but genetic analyses published in 2013 confirmed its reassignment to Dichotomyctere.
While Dichotomyctere is now the correct genus, the fish is still frequently mislabeled in the aquarium trade as Tetraodon nigroviridis.
Care should be taken not to confuse D. nigroviridis with closely related species such as D. sabahensis or D. fluviatilis, which are also often marketed under the name “Green Spotted Puffer.” Other common names in circulation include “Leopard Puffer,” “Spotted Leopard Puffer,” and “Spotted Puffer.”
Although this species requires brackish to full marine water for long-term health, it is still widely sold as a freshwater fish. This practice has sparked ongoing debates in hobbyist communities and has led to considerable confusion among new owners.
Interestingly, beyond its popularity in the aquarium world, D. nigroviridis holds scientific importance: it possesses the smallest known vertebrate genome (approximately 340 million base pairs) and has been adopted as a model organism in genetic research.
In the wild
The Green Spotted Puffer (D. nigroviridis) is distributed across coastal regions of South and Southeast Asia, from Sri Lanka through Indonesia, extending north to China. It inhabits a variety of freshwater and brackish environments, including rivers, floodplains, estuaries, and mangrove areas.
Its diet in the wild consists primarily of molluscs, crustaceans, and other small invertebrates, with occasional ingestion of plant material. Notably, some individuals may engage in lepidophagy and pterygophagy (the feeding on scales and fins of other fish), though this behaviour appears to be facultative rather than a specialised or constant trait.
As with other members of the Dichotomyctere genus, Green Spotted Puffer is euryhaline, meaning it can tolerate a wide range of salinities, from freshwater up to full-strength seawater, reflecting its estuarine and coastal adaptability
In the aquarium
The Green Spotted Puffer is one of the most frequently encountered puffers in the aquarium trade. When provided with the correct conditions, it is a hardy, long-lived species capable of thriving for a decade or more.
This is a medium-sized, highly active pufferfish that requires a spacious aquarium with both brackish to marine conditions and an aquascape designed to balance open swimming areas with secure hiding places.
We recommend scaping heavily toward the back and sides of the aquarium using rockwork or artificial structures. This creates cover and resting areas while leaving a broad, open corridor at the front for swimming. Such a layout encourages the fish to patrol the length of the tank where it can be easily observed, while still offering retreats to reduce stress.
A heavily decorated aquarium helps the Green Spotted Puffer feel secure, which in turn encourages its natural foraging, hunting, and exploratory behaviours. They will sift through crevices and graze across surfaces in search of food, so providing an engaging environment helps prevent boredom and associated aggression.
Based on hobbyist experience and observation, FOWLR (Fish-Only With Live Rock) and mangrove/mock-mangrove aquariums provide the most naturalistic and effective environments for this species. While technically reef-capable in terms of water chemistry, Green Spotted Puffer are not reef-safe; they are notorious for nipping, chewing, or outright destroying corals.
Because of their messy feeding habits and high waste output, this species requires powerful, oversized filtration (sump systems and canister filters are both effective) combined with medium to strong water movement. Supplemental flow pumps or powerheads can be used to reduce dead spots, but ensure that all intakes are covered with guards or protective cages. Green Spotted Puffer are inquisitive and may injure themselves by exploring or becoming trapped in unprotected equipment.
Regular maintenance, including large weekly water changes with premixed saltwater, is essential to maintain stable salinity and water quality.
Substrate
The Green Spotted Puffer is not a burrowing or wallowing species like some freshwater puffers, but it will frequently cruise close to the bottom of the aquarium, resting or nosing along the substrate while exploring. For this reason, a safe, smooth substrate is important to avoid abrasion of the belly, which lacks protective scales. Even minor scrapes can lead to infections in scaleless fish such as puffers.
We strongly recommend the use of a fine-grained substrate, ideally sugar-sized aragonite sand (0.5–1.7 mm grain size). This particle size mimics the sandy, silty substrates of estuarine habitats while remaining smooth enough to be safe. Aragonite sand also helps buffer water chemistry slightly toward alkalinity and stability, which can be advantageous in brackish and marine systems.
By contrast, crushed coral sand should be avoided. Its angular, sharp particles present an unnecessary risk of injury to the fish’s underside.
Similarly, coarse gravel or large substrates may appear decorative, but they present two significant drawbacks:
Waste accumulation: Large interstitial spaces allow uneaten food, fish waste, and detritus to settle deep between particles, where it escapes circulation and filtration. This can lead to localised pockets of decomposition, elevated nitrate and phosphate levels, and degraded water quality.
Flow disruption: Puffers produce heavy bioload, and the buildup of organic debris in coarse substrates can overwhelm even strong filtration. In contrast, fine sand tends to keep waste on the surface, where it remains accessible to water movement and can be more easily removed during routine maintenance.
A shallow sand bed (1–2 cm) is generally best for Green Spotted Puffer systems. This provides the aesthetic and behavioural benefits of a natural substrate while minimising the risk of anaerobic pockets forming. In larger systems with strong flow, slightly deeper beds may be used, particularly in mock-mangrove displays where rooted plants can stabilise and oxygenate the substrate.
Finally, a sandy base also supports natural foraging behaviours: the Green Spotted Puffer will often sift through sand in search of morsels, mimicking its wild behaviour in tidal flats and estuaries. Providing such opportunities enriches the aquarium and reduces the risk of stereotyped behaviour or boredom.
Tank size
With proper care, this puffer regularly reaches between 15–17 cm (6–6.7 inches) in captivity.
It is an active, high-energy swimmer that spends much of its day patrolling the aquarium, moving back and forth across the length of the tank, and investigating every corner in search of food. Its exploratory nature makes it particularly sensitive to cramped quarters, so providing sufficient space is one of the most important aspects of husbandry.
Minimum Tank Size
For a single adult, we recommend an aquarium of at least:
120 cm (47 in) length
35 cm (14 in) width
50 cm (20 in) height
This equates to roughly 200 litres (55 US gallons). The long footprint allows for straight-line swimming, which is more important for this species than extra height alone.
Housing More Than One
Although Green Spotted Puffers can sometimes be housed in groups, they are territorial and aggressive, so success depends on careful observation and providing ample space. If attempting to keep a pair, a larger footprint is essential to reduce stress and aggression. A good baseline is:
120 cm (47 in) length
48 cm (19 in) width
55 cm (22 in) height
This corresponds to a standard 290-litre (75 US gallon) aquarium.
Even at this size, keepers should be prepared for territorial disputes and have a plan to separate individuals if necessary. For each additional puffer beyond a pair, add a substantial increase in both volume and footprint, ideally moving into tanks of 450 litres (120 US gallons) or more.
Why Tank Size Matters
Activity level: Green Spotted Puffer are intelligent, restless fish. A cramped aquarium quickly leads to stress, pacing behaviour, and aggression.
Waste output: They produce a heavy bioload; larger water volumes provide more stable conditions and reduce the risk of ammonia or nitrate spikes.
Territory and enrichment: Extra space allows for meaningful aquascaping, which provides hiding places as well as open swimming areas, without crowding.
In short: if you want to see your Green Spotted Puffer at its best (actively swimming, hunting, and interacting) bigger is always better.
Salinity and Acclimation
Green Spotted Puffer are rarely sold from brackish systems. Instead, they are typically housed and shipped in freshwater, which makes them easier for retailers to manage and cheaper to sell. This practice has created widespread confusion in the hobby: many new keepers assume (or are told) that this species is a true freshwater fish, while in reality it requires brackish to marine conditions for long-term health.
The commonly recommended method is to begin with the fish in freshwater and then gradually increase salinity by ~0.002 specific gravity per week until the desired brackish or marine level is reached. The logic behind this method is that a slow change gives the fish time to adjust, and supposedly allows the existing bacterial colony to adapt alongside the rising salinity. However, this advice is flawed. The microorganisms that maintain the nitrogen cycle in freshwater (largely ammonia-oxidising archaea and nitrite-oxidising bacteria adapted to low salinity) begin to die as salt levels rise. True marine nitrifiers are different species altogether.
In many cases, the “transition” does not happen smoothly; instead, the freshwater colony perishes before a stable brackish/marine colony can establish. This can leave the aquarium with little or no biological filtration, which can easily result in ammonia or nitrite spikes and fish mortality.
For this reason, we do not recommend raising salinity in a cycled freshwater aquarium containing fish. The risk of a mid-transition cycle crash is simply too high.
The safest and most reliable method is as follows:
Cycle the tank as brackish from the start. Prepare your aquarium at the target salinity (at least SG 1.005 or higher, depending on the age/size of the puffer). Seed the filter media with hardy brackish-tolerant bacteria, or use live rock if starting closer to marine.
Confirm the cycle is complete. Ammonia and nitrite must both read zero for at least 1–2 weeks under a normal feeding load.
Bring your Green Spotted Puffer home and drip acclimate it slowly to the pre-cycled brackish aquarium. This reduces osmotic shock while placing the fish immediately into a biologically stable system. Laboratory studies show that Green Spotted Puffer (Dichotomyctere nigroviridis) can be transferred directly from freshwater to seawater rather quickly without mortality, as their gills and kidneys rapidly adjust to the change in salinity. This means the fish itself can tolerate salinity shifts remarkably well. The real challenge is not the puffer, but the aquarium’s filtration system.
As a guideline, juveniles under 6 cm do well at a specific gravity of 1.007–1.012 (9–16 ppt), sub-adults around 6–10 cm should be kept at 1.012–1.018 (16–24 ppt), and adults above 10 cm thrive at 1.018–1.025 (24–33 ppt). Full marine conditions (SG ~1.025) are tolerated perfectly well by adults, as demonstrated in laboratory trials. Always measure salinity with a calibrated refractometer, and mix marine salt thoroughly before use.
In summary, the fish itself is highly adaptable, but the filtration system is fragile. By cycling the aquarium at the intended salinity and drip acclimating your puffer into it, you avoid the risks of a cycle crash, protect the fish from toxic ammonia or nitrite, and give your Green Spotted Puffer the stable brackish or marine environment it needs to thrive.
The Bucket Cycle Method
If you cannot prepare a full brackish display tank in advance, there is still a reliable alternative. You can use a large food-safe bucket or storage tub as a temporary cycling station, with the fish in the freshwater display. This allows you to establish a stable brackish biofilter in a separate body of water.
Step 1 — Prepare the container
Choose a sturdy, food-safe bucket or tub (20–40 L minimum).
Fill it with water at the same salinity you intend for the eventual display tank.
Add a heater and aeration if needed to maintain stable temperature and oxygen levels.
Step 2 — Install a filter
Run a filter you intend to use on the display tank (e.g. canister, hang-on-back, etc) directly in the bucket.
This ensures the filter media becomes colonised with brackish-tolerant bacteria.
Step 3 — Begin a fishless cycle
Dose the bucket with pure ammonia to around 2–3 ppm.
Test daily. Ammonia should begin to drop as bacteria establish, followed by a rise in nitrite.
Continue “feeding” ammonia to keep the cycle alive.
Step 4 — Wait for full cycling
A full cycle is achieved when both ammonia and nitrite return to zero within 24 hours of dosing, and nitrate is present.
This usually takes 3–5 weeks, but seeding with media from an existing brackish or marine tank can speed things up significantly.
Step 5 — Transfer to the display tank
Once the cycle is proven stable, move the filter (and/or its media) from the bucket into your display aquarium, which has already been filled with water at the same salinity.
Drip acclimate your puffer to the aquarium.
Water values
Salinity:
Juveniles (<6 cm): 1.007–1.012 (9–16 ppt)
Sub-adults (6–10 cm): 1.012–1.018 (16–24 ppt)
Adults (≥10 cm): 1.018–1.026 (24–33 ppt)
pH: 7.5–8.5 (slightly alkaline at all life stages).
Temperature: 24–28 °C (75–82 °F).
Nitrate (NO₃⁻): Below 20 ppm, ideally under 15 ppm.
Hardness / Minerals: At least 8–10 dGH equivalent in freshwater or low brackish. In high brackish and marine conditions, hardness is not critical because marine salt mixes supply adequate calcium and magnesium.
Alkalinity (KH): 6–12 dKH in low brackish, 8–12 dKH in high brackish to marine. Marine salt mixes naturally maintain buffering capacity.
Tank mates
If you are looking for an interactive pufferfish with a bold personality, this species could be the perfect choice. These fish are highly intelligent, curious, and often engage directly with their keepers. However, if your goal is to keep a calm, community-safe puffer that can coexist peacefully with other species, then this species is not the right fit.
By nature, the Green Spotted Puffer are predatory and aggressive, with a strong instinct to nip fins and prey upon smaller fish. Their temperament is unpredictable, but they are far more likely to harass or kill tankmates than tolerate them long-term. For this reason, the safest recommendation is to keep them either alone or in a species-only aquarium.
It is not impossible to keep more than one Green Spotted Puffer in the same system, but doing so requires extreme caution. Their behaviour toward one another can be inconsistent; some groups settle into a hierarchy with little conflict, while others display constant aggression. If you attempt to keep multiple specimens together, follow these basic guidelines:
Equal size: Only keep puffers of a similar size to prevent bullying.
Simultaneous introduction: Add them to the aquarium at the same time so that no single fish has an established territory.
Ample space: Provide a large tank (see tank size recommendations) with extensive aquascaping, creating both open swimming space and numerous visual barriers. This reduces line-of-sight and allows individuals to avoid each other when necessary.
Close monitoring: Be prepared to separate individuals at the first sign of persistent aggression, as conflicts can escalate quickly and lead to injury or death.
Contrary to popular belief, the closely related Dichotomyctere ocellatus (Figure 8 Puffer) is not a suitable tankmate for the Green Spotted Puffer. While both belong to the same genus, their requirements and temperaments differ significantly. Green Spotted Puffer ultimately need high-brackish to marine conditions, whereas D. ocellatus thrives in lower brackish environments. Housing them together places one or both species outside of their proper range and almost always results in aggression.
In short, the Green Spotted Puffer is best enjoyed as a single-specimen aquarium fish. This setup allows it to display its full intelligence, activity, and personality without the stress of constant conflict, for both the fish and the keeper.
Sexual dimorphism
From the research and reliable aquarist reports:
No clear external sexual dimorphism has been documented in the Green Spotted Puffer.
Males and females are essentially indistinguishable in appearance: both share the same green/black spotted dorsal pattern and pale ventral colouring.
Body shape, colour intensity, or spot size have sometimes been suggested as possible indicators, but these are inconsistent and not scientifically validated.
Dissection and gonadal examination are the only reliable ways to determine sex.
Breeding in captivity is extraordinarily rare, and most aquarists consider sexing this species practically impossible without internal examination. Unlike some freshwater puffers (e.g. Carinotetraodon travancoricus), there are no dependable external traits for Green Spotted Puffer (D. nigroviridis).
Notable behavior
The Green Spotted Puffer is a remarkably intelligent and interactive species. Many keepers report that once the fish learns to associate its owner with feeding, it will beg for food, follow movements outside the glass, and even “watch” activity in the room. This high level of awareness makes them engaging aquarium residents, but it also means they require more stimulation than most fish to remain healthy and content.
Because this species is a restless, active swimmer, it should be provided with a tank that allows long, uninterrupted swimming runs. They will patrol the length of their aquarium throughout the day, often stopping to inspect structures or sift through the substrate for food. A well-designed layout that balances open swimming space with areas of cover is essential.
Mental stimulation is just as important as physical space. Green Spotted Puffer benefit greatly from environmental enrichment such as:
A varied aquascape with caves, tunnels, and visual barriers to explore.
Feeding puzzles or hiding food inside shells, crevices, or small containers.
Occasional rearrangement of rockwork or décor to create novelty in their environment.
When these needs are not met, the fish may show signs of stress or boredom. This is often reflected in unnatural swimming behaviour: repetitive pacing up and down the glass, frantic dashing, or circling patterns. Such behaviours indicate that the fish feels confined or unstimulated, and they usually resolve once the environment is improved.
Providing both space and enrichment allows the Green Spotted Puffer to display its full range of natural behaviours, exploring, hunting, and interacting with its surroundings, which is what makes this species such a rewarding aquarium inhabitant..
Feeding
At Pufferfish Enthusiasts Worldwide, we encourage all keepers to replicate the natural diet of their pufferfish as closely as possible. In the wild, the Green Spotted Puffer feeds on an exceptionally diverse range of prey, and while it isn’t possible to copy that diet exactly in captivity, we can get very close by offering a wide variety of suitable foods.
As keepers, it’s our responsibility to provide that variety. Doing so doesn’t just keep your puffer healthy; it also keeps them interested and engaged. A mix of different flavours, textures, and prey types adds vital enrichment to their daily routine, turning every meal into both nutrition and stimulation. Puffers are intelligent, curious fish, and mealtime is one of the main ways they interact with their environment.
A varied diet also ensures your Green Spotted Puffer receives the full spectrum of nutrients it needs for strong growth, vibrant colouration, and a long, healthy life. Relying too heavily on one or two food types can leave gaps in nutrition and even contribute to dental or health problems over time.
In short, feeding Green Spotted Puffer isn’t just about filling its belly; it’s about recreating the variety and challenge of its natural feeding habits. By doing so, you’ll get to watch your puffer behave in the lively, inquisitive way that makes this species so fascinating to keep.
Our preferred foods for these fish include:
Bivalves on the half-shell (cockle/clam/oyster)
Shell-on shrimp/prawn (heads/shell left on)
Crab (fiddler/shore; legs/pieces, shell on)
Snails (ramshorn/pond/marine, size-matched)
Soft marine inverts (mysis, squid krill)
Low-thiaminase white fish (e.g., cod)
Terrestrial inverts (earthworms, woodlice, small roaches/crickets; gut-loaded, pesticide-free)
Live enrichment (gut-loaded ghost shrimp etc.)
We suggest breaking down the diet (as shown in the chart) to approximately 20% Bivalves on the half-shell (cockle/clam/oyster), 15% Shell-on shrimp/prawn (heads/shell left on), 15% Crab (fiddler/shore; legs/pieces, shell on), 15% Snails (ramshorn/pond/marine, size-matched), 15% Soft marine inverts (mysis, squid, krill), 8% Low-thiaminase white fish (e.g., cod), 7% Terrestrial inverts (earthworms, woodlice, small roaches/crickets; gut-loaded, pesticide-free), and 5% Live enrichment (gut-loaded ghost shrimp etc.).
Quick notes
Rotate daily so no single item becomes the staple.
Not any one food should make up more than 20% of the fish's overall diet.
Keep at least 3 shell-on meals/week (adults), 2–3/week (juveniles).
Always gut-load terrestrial inverts.
Use human-grade seafood where possible.
If collecting live foods, freeze to sushi standards before feeding to reduce parasite risk: −20 °C for 7 days or −35 °C for 15 hours (then hold cold).
Filtration and tank maintenance
The Green Spotted Puffer is highly intolerant of poor water conditions, and maintaining excellent water quality is one of the most important aspects of its care. These puffers are messy eaters with a heavy protein diet, and they produce significant amounts of waste. Left unchecked, this organic material rapidly breaks down into ammonia, nitrite, and ultimately nitrate. Because puffers are scaleless and particularly sensitive to toxins, even moderate lapses in water quality can quickly lead to stress or illness.
For this reason, a high level of both biological and mechanical filtration is essential. Mechanical filtration removes uneaten food and suspended debris before it decays, while biological filtration provides the nitrifying bacteria needed to detoxify ammonia and nitrite. Both work together to provide the stable, clean conditions that this species demands.
Strong filtration alone is not enough, however. Good husbandry is just as critical. Frequent partial water changes must be performed to export nitrates and dissolved organics, with a goal of keeping nitrate levels consistently below 15 ppm. This threshold is more conservative than what many marine fish will tolerate, but puffers thrive when nitrates are kept low.
Regular siphoning of waste from the substrate, along with prompt removal of uneaten food, will also help prevent nutrient buildup.
For long-term success, we strongly recommend the use of a protein skimmer in medium- to high-brackish or marine systems. A protein skimmer works by stripping out dissolved organic waste before it has the chance to break down into ammonia or nitrate. This not only improves water quality but also increases oxygenation, creating a healthier environment overall. A properly sized and well-tuned skimmer can make the difference between constantly battling high nitrate levels and maintaining a stable, low-nutrient system.
Inflation
Like other pufferfish, the Green Spotted Puffer has the remarkable ability to inflate its body by rapidly drawing in water (or sometimes air if removed from the tank). This is a natural defensive mechanism used in the wild to deter predators by making the fish appear much larger and more difficult to swallow.
While impressive to witness, inflation is a sign of fear or severe stress, not a display to be encouraged. Forcing or provoking a puffer to inflate can be extremely harmful. The act itself is physically demanding, and repeated or unnecessary inflations may weaken the fish, compromise its health, and reduce its lifespan.
In addition, if the fish inflates with air instead of water (such as during handling), it may have difficulty expelling the air, which can cause buoyancy issues or even be fatal.
For these reasons, keepers should never deliberately provoke their puffer into inflating. The goal in the aquarium is to create an environment where the fish feels secure and relaxed, making inflation a rare event. If your puffer does inflate, it usually means it has been startled or feels threatened. In such cases, the best response is to remain calm, avoid further disturbance, and allow the fish time to settle.
In short: inflation should be treated as an emergency behaviour, not a form of entertainment. With proper care, a Green Spotted Puffer will spend its life confident, active, and interactive without ever needing to resort to this defensive display.
