Green Spotted Puffer

Geographical Origin & Biotope:

The native distribution of *Dichotomyctere nigroviridis* (formerly *Tetraodon*) spans a vast area of continental and insular Southeast Asia, from the coasts of India to Sri Lanka, Myanmar, Thailand, down to Indonesia and the Philippines. It is a euryhaline species, inhabiting the intricate and extensive systems of estuaries and river deltas where freshwater meets the sea, especially in lush and warm mangrove forests, an environment characterized by strong daily salinity swings caused by tides.

Taxonomy & Morphology:

The scientific name of the genus has recently been revised, although in the hobby it is still almost universally known as *Tetraodon* (from Greek, "four teeth", which make up the beak). The body, up to 17 cm (7 inches) long, is club-shaped and lacks true pelvic fins, which gives it that characteristic and comical way of swimming, akin to a hovering helicopter, using its pectorals, dorsal, and anal fins at supersonic speeds to turn on the spot or swim backward. In case of danger, the highly elastic stomach fills with water, tripling the fish's size.

Social Behavior:

They are benthic predators with an IQ far above the norm for fish. They quickly memorize feeding times, their owner, and the position of objects, and they get bored easily if the tank is too bare (going up and down the glass, the so-called "glass surfing"). They are curious to the point of meticulously exploring every single crevice and nook.

Coloration & Sexual Dimorphism:

The coloration of the back and flanks varies from a bright chartreuse yellow to a rich fluorescent emerald green (depending on mood), covered with large, irregular velvety black polka dots. The belly, in conditions of health and without stress, is a pure, bright snow-white; a grey, dark greyish, or black-spotted belly is their signal of malaise, illness, or water stress. The eyes, large and capable of moving independently of each other like a chameleon's, have a golden-green or red iris. Sexual dimorphism is visually absent.

Tank Setup:

The greatest challenge with the GSP is the environment. It is a fish born in mangrove estuaries. A juvenile bought at 3 cm (1 inch) can survive in freshwater for a few months, but without the progressive transition to brackish water (and subsequently marine in adulthood), its immune system will collapse. The setup requires synthetic marine salt (not table salt). For an adult specimen (up to 17 cm / 7 inches) a 150-liter (40-gallon) tank is needed with a specific gravity between 1.015 and 1.020 measured with a refractometer. The layout must abound in limestone rocks, dead corals, and mangrove roots. Highly salted water precludes the use of almost all live plants, making the use of synthetic decor or macroalgae the only layout option.

Diet & Feeding:

The mouth of this fish is not composed of individual teeth, but of bony plates fused to form a powerful parrot-like beak in continuous and rapid growth. If fed flakes or soft foods, the teeth will grow until they fuse shut, preventing the fish from opening its mouth and condemning it to starve. The diet *must* include hard shells: freshwater snails (Physa, Planorbis, Melanoides) offered daily, pieces of crab claws, crushed mussels with the shell, whole dried krill, and shrimp. Oysters or clams served on the half shell are perfect for them to file their beaks on. They are chronic gluttons: stop feeding before their belly takes on the appearance of a tight balloon, feeding them every other day as adults.

Water Quality:

Like most pufferfish, *nigroviridis* lacks scales and covered gills, and is therefore pathologically sensitive to toxins. Ammonia and nitrites (lethal at very low doses) and high nitrates will cause their white belly to darken and induce chronic lethargy. The biological filter in brackish water must be oversized, with a protein skimmer (if at near-marine density) and titanic water changes. Maintain a constant temperature between 24 and 28°C (75-82°F) and a strongly alkaline pH (7.5-8.5).

Compatibility & Tankmates:

The cute, chubby little face hides a psychopathic predator. It has an unstoppable tendency to bite and tear pieces of fin or flesh from any fish that swims slowly enough to be approached, inflicting devastating circular wounds. Cohabitation with small fish (neons, guppies) will result in their annihilation. The vast majority of GSPs live happily alone in a species-only tank for 10-15 years. Only in immense tanks (500+ liters / 130+ gallons) can cohabitation be attempted with very fast and large brackish fish like Scats or brackish moray eels, provided massive rocky visual interruptions are created.

Aquarium Breeding:

There are no reliable, documented reports of breeding in domestic or amateur commercial aquariums. It is assumed that they are substrate spawners and that, in their natural cycle, juveniles migrate from rivers to the open sea as they mature, requiring enormous open spaces and salinity variations to trigger reproductive behaviors.

Risks & Diseases:

The greatest risk stems from osmotic stress: keeping them in pure freshwater will inexorably lead to renal collapse, color fading, and chronic susceptibility to Ich (white spot) or external parasites. Furthermore, like all pufferfish, if they are scared to death or pulled out of the water, they will swallow air or water to puff up as a defense: swallowing air out of water can be fatal if they cannot expel it, floating inexorably upside down. For transfers, use rigid containers, never nets.