Figure 8 Puffer

Also known as: Tetraodon biocellatus

The Figure 8 Puffer (Tetraodon biocellatus) is a small, distinctive freshwater pufferfish named for the dark, figure-eight pattern on its back. The Figure 8 Puffer originates from Southeast Asia, specifically found in freshwater and brackish waters of Thailand, Malaysia, Indonesia, and parts of Borneo, often in slow-moving rivers, estuaries, and mangrove swamps., reaches 8 cm in captivity, typically lives 10, and is kept at 24C (75F). Individual fish vary, so treat this as a general guide rather than a guarantee.

Species at a glance

Origin: Southeast Asia, specifically found in freshwater and brackish waters of Thailand, Malaysia, Indonesia, and parts of Borneo, often in slow-moving rivers, estuaries, and mangrove swamps.
Adult size: 8 cm (3.1 in)
Life span: 10
Temperament: Semi-aggressive and territorial, especially toward conspecifics and similarly shaped fish; best kept singly or in very large tanks with careful monitoring.
Tank size: 75 L (20 gal)
Water temp: 24C (75F)
pH range: pH 7.0-8.0
Diet: Carnivorous; requires hard-shelled foods like snails, crustaceans, and mollusks to wear down continuously growing teeth, supplemented with frozen or live bloodworms, brine shrimp, and high-quality carnivore pellets.
Other names: Tetraodon biocellatus

About the Figure 8 Puffer

The Figure 8 Puffer (Tetraodon biocellatus) is a small, distinctive freshwater pufferfish named for the dark, figure-eight pattern on its back. It is native to Southeast Asian brackish and freshwater habitats and is known for its curious, intelligent behavior and ability to inflate when threatened. This species requires specific dietary needs to prevent dental overgrowth and is not recommended for beginner aquarists due to its sensitivity to water quality and aggressive tendencies. Despite its small size, it demands careful tank management and specialized feeding to thrive in captivity.

Lifespan and health

With proper care, Figure 8 Puffers typically live 8–12 years in captivity, with some individuals reaching up to 15 years under optimal conditions. Longevity is heavily influenced by diet, water quality, and stress levels; consistent access to hard-shelled foods to prevent dental overgrowth is the single most important factor in extending lifespan. Poor nutrition leading to overgrown teeth can result in inability to eat, requiring veterinary trimming under anesthesia—a procedure that carries risk and stress. Regular monitoring of eating behavior and mouth condition is essential for early detection. Common health issues include dental overgrowth (malocclusion), bacterial infections (often from poor water quality or injury), parasitic infestations (such as ich or flukes), and stress-related ailments from incompatible tankmates or inadequate hiding spots. Signs of distress include lethargy, loss of appetite, clamped fins, rubbing against objects (indicating parasites), or visible tooth overgrowth. Maintaining stable water parameters (ammonia and nitrite at 0 ppm, nitrate <20 ppm), providing a varied diet rich in hard-shelled prey, and minimizing stressors are key to preventing disease. Quarantine new arrivals for 2–4 weeks and avoid copper-based medications, as puffers are highly sensitive to them.

Overview

Care and tank setup

Tank setup should include a minimum 75-liter (20-gallon) aquarium with a sandy substrate to allow for natural foraging behavior, plenty of hiding places using driftwood, rocks, and dense planting (such as Java fern or Anubias), and moderate water flow to mimic estuarine conditions. A tight-fitting lid is essential as these fish are known to jump. Water parameters must be maintained within a pH range of 7.0–8.0 and temperature of 24–26°C (75–79°F); while they can tolerate freshwater, long-term health is improved in low-end brackish conditions (specific gravity 1.003–1.005) using marine salt mix, though abrupt changes should be avoided. Filtration should be robust to handle their waste output, with weekly 25% water changes to keep nitrates below 20 ppm. Feeding is critical for dental health: offer hard-shelled foods like live or frozen snails (ramshorn, pond snails), small crustaceans (daphnia, brine shrimp), or crushed mussels 2–3 times per week to prevent overgrown teeth, which can lead to starvation if not trimmed. Supplement with high-protein frozen foods like bloodworms or mysis shrimp 2–3 times weekly, and avoid relying solely on soft pellets or flakes. Feed only what they can consume in 2–3 minutes, removing uneaten food promptly to maintain water quality. Overfeeding is a common cause of obesity and poor health. Tankmates should be chosen with extreme caution due to their semi-aggressive nature; they are best kept alone. If attempting community housing, only fast, short-finned, upper-water-column species like certain danios or rainbowfish may be tolerated in very large tanks (150L+/40G+), but even then, fin-nipping or territorial chasing is common. Avoid slow-moving, long-finned, or bottom-dwelling fish (e.g., bettas, guppies, corydoras) as they are likely to be harassed or injured. Never house with other puffers unless the tank is enormous (300L+/80G+) and heavily decorated to break lines of sight.

Adding a Figure 8 Puffer? Research the species’ adult size and temperament carefully, quarantine new fish before introducing them to your tank, and buy from reputable aquarium stores or breeders.

Breed information on this page is based on the Wikipedia article on the Figure 8 Puffer, supplemented with additional research. Reviewed for accuracy.