The Figure 8 Pufferfish, scientifically named Tetraodon biocellatus, is a small, freshwater puffer known for its unique markings and intriguing personality. Native to the freshwater and brackish waters of Southeast Asia, this pufferfish draws attention with its distinctive 'figure 8' pattern and interactive behavior, making it a favorite among aquarists who appreciate its quirky nature and expressive eyes.

Overview and Appearance:
- Scientific Name: Tetraodon biocellatus
- Family: Tetraodontidae
- Size: Up to 3 inches (7.5 cm)
- Lifespan: 5-10 years in optimal conditions

The Figure 8 Puffer's body is stout and, when threatened or excited, can inflate into a near-spherical shape. Its base color ranges from a yellowish to olive tone, decorated with dark spots and a distinctive 'figure 8' or 'eye-spot' pattern, which helps in deterring predators by confusing them about the puffer's orientation.

Habitat and Tank Requirements:
Mimicking the Figure 8 Puffer's natural environment is essential for its well-being:
- Water Parameters: Slightly acidic to neutral pH (7.0-7.5), with a temperature range of 74-79°F (23-26°C). They can tolerate a range of salinities but prefer brackish conditions.
- Tank Setup: A minimum tank size of 15-20 gallons for a single puffer. The tank should be well-planted with plenty of hiding spots and open space for swimming. Soft substrate is preferred to prevent injury to the puffer's delicate underbelly.
- Filtration: Robust filtration is necessary to handle the high bioload and maintain water quality. Regular water changes are also crucial.

Diet and Nutrition:
Figure 8 Puffers have a beak-like structure that continuously grows and needs to be worn down by eating hard-shelled foods:
- A diet primarily composed of snails, shellfish, and crustaceans to maintain beak health.
- Occasional offerings of frozen or live foods like bloodworms and brine shrimp for variety.
- Avoid overfeeding, as puffers are prone to obesity and related health issues.

Behavior and Compatibility:
Figure 8 Puffers are known for their intelligence and can become quite interactive with their owners. However, they are also territorial and can be aggressive towards tank mates:
- Best kept singly or with other fast-moving, brackish water fish that can hold their own.
- Avoid housing with slow-moving or long-finned fish, as puffers may nip fins or attack them.
- Monitor interactions closely if keeping with other fish, as their temperament can vary.

Breeding:
Breeding Figure 8 Puffers in captivity is quite challenging and not commonly achieved:
- Requires precise water conditions and a large, well-structured tank.
- Identifying sexes is difficult, and providing an environment that mimics their natural breeding conditions is complex.

The Figure 8 Pufferfish offers a unique blend of beauty, personality, and complexity. While its care requirements, especially regarding diet and tank specifications, demand attention and dedication, the reward is a truly interactive and captivating aquarium inhabitant. With proper care, the right environment, and a watchful eye on their social interactions, the Figure 8 Puffer can become the centerpiece of an aquarist's collection, offering daily engagement and a window into the fascinating behaviors of one of the aquatic world's most personable species.