Figure 8 Puffer (Eyespot puffer)

1) Where they come from (the quick backstory)

Figure 8 puffers come from slow rivers, estuaries, and mangrove-y areas in Southeast Asia (Thailand/Malaysia/Indonesia region). Think "freshwater mixing with seawater," lots of roots, leaf litter, and little critters to hunt. That’s why they’re brackish fish in the hobby, even if the store tank looks like plain freshwater.

2) Setting up their tank

Give them space and stuff to explore. A single Figure 8 can live in a 15–20 gallon, but 20 long is way nicer because they cruise and investigate everything. If you’re thinking about multiple puffers, go bigger and expect some drama anyway.

Brackish doesn’t mean "a pinch of salt." Use marine salt mix (not aquarium/tonic salt) and actually measure it with a refractometer or hydrometer. I’ve had the best long-term results keeping them at a steady low brackish level rather than bouncing around with random salt doses.

• Tank size: 20 gal for one (recommended); 15 gal minimum if you’re disciplined with maintenance
• Salinity: aim around SG 1.005–1.010 (stable matters more than chasing a magic number)
• Temp: mid-to-high 70s °F (24–27°C)
• Filtration: they’re messy eaters—oversize your filter and plan on regular water changes
• Substrate/decor: sand or fine gravel, driftwood/roots, rock piles, caves, lots of line-of-sight breaks
• Plants: tough options like Java fern/Anubias can work at low brackish; many plants melt as salinity rises

3) What to feed them

They’re hunters, not pellet grazers. Some will learn to take frozen, but many Figure 8s stay picky. Variety is the trick—if you feed one thing over and over, they’ll either refuse later or start looking rough.

The big puffer-specific thing: teeth. If you don’t offer crunchy foods, their beak keeps growing and eventually they can’t eat. I try to work in snails or shelled foods regularly.

• Staples: live/frozen snails (pond/bladder/ramshorn), frozen bloodworms, brine shrimp, mysis
• Great "crunch": small ramshorns, Malaysian trumpet snails, chopped clam/mussel in shell, cockle
• Occasional: earthworms (rinsed well), blackworms, small pieces of shrimp or fish (not all the time)
• Usually a miss: flakes (they spit it out) and random "puffer pellets" (some take them, many don’t)

4) Behavior + tankmates (the honest version)

Figure 8s have huge personality. They watch you, beg, and act like tiny wet dogs. They’re also nippy and get bored easily. A bored puffer will redecorate the tank and test-bite anything that moves.

Tankmates are a gamble. Some individuals are surprisingly chill, and some are little torpedoes with teeth. If you want the least stress, keep one puffer as the centerpiece and call it a day.

• Best tankmate: another setup (a species tank is easiest)
• Risky but sometimes works: fast, sturdy brackish fish with short fins (some monos/scats are too big and need higher salinity later)
• Usually ends badly: slow fish, long fins, bottom sitters, anything that can’t get away
• Guaranteed snacks: shrimp, snails you want to keep, most small crabs

5) Breeding tips (realistic expectations)

Breeding Figure 8 puffers in home tanks isn’t common. Sexing them is tricky, and getting a compatible pair is the hard part. Most hobbyists keep singletons, so breeding talk is mostly "cool trivia" rather than something you’ll accidentally stumble into.

If you do want to try: you’ll need a well-fed group to let pairs form, lots of cover, and top-notch water. They’re egg scatterers, and adults may snack on eggs/fry, so you’ll want a plan to separate or collect eggs.

6) Common problems to watch for

Most Figure 8 issues come from three things: wrong/unstable salinity, dirty water (they’re messy), and diet problems. Catch stuff early and they’re surprisingly hardy.

• Overgrown teeth: refusing food, picking and spitting, weight loss (fix with more crunchy foods; severe cases need trimming by an experienced keeper/vet)
• Skinny new fish: often parasites or just not eating in a new tank (offer live foods like snails/blackworms and keep stress low)
• Ich/white spot: can happen, especially on new arrivals—treat carefully and research meds (puffers can be sensitive; avoid copper unless you truly know what you’re doing)
• Fin/nose scrapes turning into infections: usually from sharp decor or ammonia/nitrite problems
• Bloating: sometimes constipation from a poor diet; sometimes something more serious—try fasting a day and offering shelled foods, and check water quality