Figure 8 Puffer (Dichotomyctere ocellatus)

The Figure 8 Puffer (Dichotomyctere ocellatus) is a highly intelligent, interactive, and visually striking brackish-water fish popular among intermediate aquarists. Known for its expressive, independently moving eyes and curious behavior, it quickly learns to recognize its owner and will actively beg for food at the glass.

Critical Water Parameters

While local pet stores often mistakenly sell them as freshwater fish, keeping a Figure 8 puffer in pure freshwater severely shortens its lifespan and causes chronic stress. They require low-salinity brackish water to thrive long-term.

Salinity / Specific Gravity: 1.005 to 1.008 SG (achieved using Marine Salt, not aquarium salt)

Temperature: 24°C to 28°C (75°F to 82°F)pH Level: 7.5 to 8.3 (alkaline, hard water)

Water Quality: Ammonia and Nitrites must be strictly at 0 ppm, with Nitrates below 20 ppm.

Diet and Continuous Tooth Growth

Figure 8 puffers are dedicated carnivores with fused, beak-like teeth that grow continuously throughout their lives. They must be fed hard-shelled foods to naturally grind down their teeth; otherwise, the beak will overgrow, locking their jaw and leading to starvation.

Essential Foods: Small snails (Pond snails, Ramshorn snails), unpeeled shrimp, krill, crabs, clams, and mussels.

Soft Meaty Foods: Bloodworms, blackworms, and earthworms (use these as supplements, not primary diets).

Note: They will completely ignore standard fish flakes or pellets.

Tank Size & Setup Requirements

Minimum Tank Size: 15 to 20 gallons (approx. 60–75 liters) for a single puffer. Add an extra 10 gallons for each additional puffer.

Filtration: Over-filtration is mandatory. Puffers are exceptionally messy eaters, leaving behind heavy organic debris that can rapidly foul water quality.

Decor: Use an aragonite or crushed coral sand substrate to naturally buffer the pH upward. Provide plenty of visual breaks using rocks, caves, and sturdy fake or brackish-tolerant plants to keep this intelligent fish from getting bored.

Safety: Always secure the aquarium with a tight-fitting lid, as puffers are notorious jumpers when startled.

Compatibility & Tank Mates

Figure 8 puffers are generally semi-aggressive and are notorious fin-nippers. They are best kept alone in a species-only display. If you choose to attempt a community setup, you must use a larger tank with fast-moving, short-finned brackish species.

Acceptable Tank Mates: Bumblebee Gobies, Knight Gobies, or Mollies.

Species to Avoid: Avoid long-finned fish (like guppies) or highly aggressive brackish fish (like Green Spotted Puffers, which grow much larger and can easily overpower a Figure 8).