Amazon Puffer (Colomesus asellus)

Common Name

Freshwater Puffer, Amazon Puffer, South American Puffer

Scientific Name

Colomesus asellus

Origin and Habitat

Colomesus asellus is native to the Amazon and Orinoco basins, with records from Brazil, Peru, Colombia, and Bolivia, and in several Guiana drainages. It lives in true freshwater, not brackish. In the wild it cruises river channels, flooded forest edges, and calm side creeks with sand or fine gravel, submerged roots, driftwood, and seasonal leaf litter. Flow is gentle to moderate and the water can be clear or tea stained with tannins. Oxygen is high and the habitat is rich in snails, small crustaceans, and insect larvae.

Temperature and Water Conditions

Preferred temperature is 75 to 82 F, about 24 to 28 C. In the wild the pH is often slightly acidic to neutral, roughly 6.0 to 7.5, with soft to moderate hardness. Stable parameters are far more important than chasing exact numbers, only adjust for special breeding projects. Keep the water very clean, well filtered, and well oxygenated. Puffers are sensitive to ammonia and nitrite, so mature filtration and regular water changes are essential.

Appearance and Size

This is a compact, energetic puffer with big curious eyes and a very cute, expressive face. The body shows alternating dark saddle bands across the back over a yellow to olive ground, with a pale belly and a bright lemon tail that really pops under good light. Fins are mostly clear except for the tail which often shows strong yellow. Sexual differences are subtle. Females tend to be rounder when full of eggs, while males may appear slightly slimmer. Maximum length is about 9 cm, roughly 3.5 inches, with most adults a little smaller.

Diet in the Wild

A specialist micro predator and shell cracker. It eats snails, small clams, insect larvae, tiny crabs and shrimp, and other crunchy invertebrates. The constantly growing beak is worn down by biting through shells.

Feeding in Captivity

Plan a menu that keeps the beak trimmed and the fish engaged. Offer pond snails, ramshorn snails, bladder snails, and trumpet snails from your own clean cultures. Add mussel or clam on the half shell, pieces of shrimp with the shell on, crab leg bits, and krill. For variety use frozen bloodworms and blackworms, and high quality carnivore pellets as a small part of the rotation. Feed small amounts twice daily and include one light feeding day each week. Many keepers maintain a simple snail breeding tub so there is always a safe, clean source of crunchy food. There are also reports that placing snails on flat stones or small plates makes it easier for puffers to bite naturally, which helps keep the beak properly worn.

Behavior and Tank Setup

Amazon puffers are lively and very personable. A happy group behaves like a tiny squadron, investigating everything with those big eyes, which is half the fun of keeping them. Kept in a proper group they are focused on each other and on foraging, which greatly reduces nipping. A group of six or more is ideal. For a larger group, a tank of 40 to 55 gallons or more with a long footprint works well. Provide open swimming lanes, fine sand, rounded stones, robust plants, and driftwood with shaded nooks. Use moderate flow and strong, matured filtration with abundant oxygen. Tank mates should be quick, similarly sized river fish without long trailing fins. Think active tetras, rasboras, and similar swimmers. Avoid slow fish with showy fins and avoid small ornamental shrimp or fancy snails, which will be treated as food. Use a tight lid since puffers can jump when startled.

Breeding

Captive breeding is very difficult. In nature this species likely spawns seasonally during rising water, scattering eggs among grasses and flooded plants with no parental care. For a hobby attempt, work with a well conditioned group, simulate a rainy season with cooler fresh water changes, a slow rise in water level, and a bit more flow, and provide dense fine leaved plants and spawning mops. If eggs appear, remove the adults or move the eggs to a separate container. The eggs are tiny and the larvae behave like plankton for a period, so early rearing benefits from very clean water, high oxygen, and constant access to microscopic live food. A green water style setup rich in micro life is helpful, with rotifers or Paramecium as first foods, followed by newly hatched brine shrimp once the fry are big enough. Some professional reports have noted better early survival for larvae in slight brackish conditions, then a gradual return to freshwater as the juveniles grow. Expect low yields and be prepared for daily small water changes and careful feeding.

Quick Facts

• Scientific name: Colomesus asellus
• Common names: Freshwater Puffer, Amazon Puffer, South American Puffer
• Origin: Amazon and Orinoco basins and nearby drainages
• Adult size: up to 9 cm, about 3.5 inches
• Temperature: 75 to 82 F preferred
• Wild pH: about 6.0 to 7.5, soft to moderate hardness
• Temperament: active, curious, very cute personality, best in a group, can nip if kept alone or bored
• Diet: snails and other crunchy invertebrates, plus meaty frozen foods
• Tank size: larger footprint tanks are best for groups, strong filtration and high oxygen
• Breeding: rare in captivity, seasonal scatter spawner, fry need microscopic live foods and very clean water, some success reported with slight brackish rearing early on
• Special care: provide regular shell bearing foods to manage beak growth, keep parameters stable rather than chasing exact numbers

Tropical Fish Co. Notes

This is one of our favorite personality fish. They are adorable and inquisitive, and a content group will follow you along the glass like a little patrol. The key is enrichment and a proper group. Give them room to cruise, keep the water sparkling, and make feeding time engaging with shell on foods they can work on. We remind new owners that the beak is normal and it must meet shell resistance often enough to stay trimmed. A simple snail culture solves that and doubles as fun hunting enrichment. For tank mates, speed and simplicity win. Choose quick schooling fish and avoid long fins. If you want shrimp or fancy snails in your life, keep them in a different aquarium. For breeding projects, plan ahead for fry food cultures and keep parameters steady, then layer in seasonal changes. Clean, stable water and thoughtful feeding routines will take you far with this charming species.