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

Endemic to Kerala and southern Karnataka in the Western Ghats of Southwest India. Distributed across several river systems including the Pamba, Chalakkudy, Periyar, Kabani, Bharathapuzha, Vamanapuram, and Muvattupuzha rivers, as well as Vembanad Lake and kole wetlands. First described by Hora and K.K. Nair in 1941 as Tetraodon travancoricus. The species name travancoricus refers to Travancore, the historical name for southern Kerala. IUCN Vulnerable due to habitat loss and extensive collection for the aquarium trade. Most trade specimens are still wild-caught (academic sources). At a maximum total length of 3.5 cm, one of the smallest pufferfish in the world. Dwells at the bottom of heavily vegetated waterways and, unlike many pufferfish species, is found in large groups in the wild. Predatory, territorial, and aggressive in aquariums despite the small size; best kept in a species-only setup. Males reach first maturity at roughly 18 mm total length (Pampa River study). Peak spawning in the wild occurs May through August, coinciding with the Southwest monsoon. Closely resembles the related Carinotetraodon imitator, which was not recognized as a separate species until 1999.

Breeding

Breeds in aquariums, though not as easily as livebearers or egg-scattering tetras. A pair or small group in a densely planted tank with Java moss or similar fine-leaved plants provides the conditions. Males display to females with lateral body compression and color intensification. Eggs are deposited individually among moss and fine plant material. Clutch size is small: 5-15 eggs per spawning. Eggs are tiny and transparent, making them difficult to find. Hatching takes 3-5 days. Fry are minuscule and need infusoria or paramecium for the first week before graduating to baby brine shrimp. Parental care is absent; adults will eat eggs and fry they find. In a heavily planted tank, some fry survive unnoticed. Dedicated breeding requires a separate rearing tank and live food cultures. Sexing is necessary because two males in a small breeding tank will fight instead of spawn. The species is increasingly captive-bred, which reduces pressure on wild populations.

Common problems

Overgrown teeth (beak) if the diet doesn't include hard-shelled food like snails. The beak plates grow continuously and need to be worn down by crunching snail shells. An overgrown beak prevents the puffer from opening its mouth enough to eat, and eventually causes starvation. If this happens, the teeth can be trimmed by an experienced keeper using a small pair of clippers under anesthesia (clove oil), but it's stressful for the fish and best prevented through diet. Internal parasites are very common in wild-caught specimens, showing as progressive wasting, white stringy feces, and a sunken belly. Treat with praziquantel and/or levamisole before adding to the display tank. Quarantine all new pea puffers for at least 2 weeks and deworm prophylactically. Fin nipping of tankmates is behavioral, not a disease, and the only cure is removing either the puffer or the victims. The species is also susceptible to ich, which shows as tiny white dots on the body; puffers are scaleless and sensitive to medication, so treat with heat (30°C for 3 days) as a first line rather than chemicals.

Bioload

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size