Pea puffer

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: any.

Behavior

Plant interaction: plant safe.

Feeding

Obligate carnivore that requires live or frozen food. Does not eat dry food (flake, pellets) and will starve rather than accept it. Staple foods: live or frozen bloodworm, live snails (ramshorn, bladder, pond snails), frozen brine shrimp, frozen mysis shrimp, live blackworms, live daphnia. Snails are important for dental health; the crunching action wears down the beak-like teeth that grow continuously (like a rodent's teeth). Without hard food to wear the teeth, the beak can overgrow and prevent the puffer from eating. Feed daily, small amounts. Target-feeding with tweezers or a pipette helps in community setups where other fish might steal the food. Pea puffers are curious and will learn to associate the tweezers with food within a few feedings.

Compatibility

• Aggressive and territorial despite their tiny size (2.5 cm). Pea puffers bite fins, chase tankmates, and claim territory with a tenacity that belies their body. Most community tank attempts with pea puffers fail because the puffer decides every other fish is either a rival or a target.
• Best kept species-only. A single pea puffer in a 20–30 L planted tank is the simplest setup. Groups work in larger tanks (40 L) with heavy planting and multiple sightline breaks. One male per 15–20 L is a rough stocking guide. Males fight; females are slightly more tolerant of each other.
• If attempting community housing, the only tankmates that sometimes work are fast, short-finned fish that stay in different zones: otocinclus (fast enough to flee, armored, different feeding zone), kuhli loaches (hide during the day when puffers are active, different activity period). Success varies by individual puffer temperament.
• Snail destroyers. Pea puffers eat snails as a primary food source and will eliminate a pond snail or ramshorn population in a tank within days. This is sometimes the reason people buy them.

Origin and habitat

Carinotetraodon travancoricus, the pea or dwarf puffer, is the smallest pufferfish kept in the hobby and one of the smallest anywhere, endemic to the rivers and wetlands of the Western Ghats in Kerala and southern Karnataka, southwest India. Hora and Nair described it in 1941 as Tetraodon travancoricus, the species name pointing to Travancore, the old name for southern Kerala. It is a true freshwater puffer, not a brackish one, living among dense vegetation and, unusually for a puffer, often in large groups in the wild. IUCN lists it as Vulnerable, with habitat loss and heavy collection for the trade as the pressures, and much of the trade is still wild-caught, though captive breeding is growing. It reaches about 2.5 cm, with a maximum near 3.5 cm. Like other puffers it has scaleless skin and fused, beak-like teeth that grow throughout life. It closely resembles the related Carinotetraodon imitator, which was not separated as its own species until 1999.

Breeding

Pea puffers will breed in a planted aquarium without much fuss once a well-fed group is held at a steady temperature. The male displays to the female, who lays small, transparent eggs singly among java moss and fine plants. Clutches are small, on the order of a dozen, and the eggs are hard to spot. There is little or no parental care, and adults eat eggs and fry they come across, so dense moss helps some survive, while serious breeding means a separate rearing tank and live food cultures. The eggs hatch in four to five days, and the fry are tiny and need infusoria-grade food before baby brine shrimp. Sexing matters, since two males in a small tank fight rather than spawn.

Common problems

Two problems stand out. The first is the beak: the fused teeth grow continuously and have to be worn down on hard-shelled food, mainly snails, or they overgrow until the fish can no longer feed; an overgrown beak can be trimmed by an experienced keeper under clove-oil sedation, but prevention through diet is far better. The second is parasites: wild-caught pea puffers very often carry internal worms that show as wasting, a sunken belly, and stringy white waste, so new fish should be quarantined and dewormed before they meet anything else. The aggression toward tankmates is behavioural rather than a disease, and the only fix is separation. Their scaleless skin also makes them sensitive to copper and many ich medications, so ich is best tackled first with heat rather than chemicals.

Bioload

Further reading

• Fish that recognize their owners