Exodon Tetra (Exodon paradoxus)

Also known as the bucktooth tetra, Exodon paradoxus is a highly aggressive and predatory schooling fish, very different from typical tetras. It’s best suited for species-only tanks or with robust tank mates that can handle their aggressive nature.

Basic Information:

• Scientific Name: Exodon paradoxus

• Common Names: Bucktooth Tetra, Exodon Tetra

• Family: Characidae

• Origin: Found in South America, mainly in the Amazon and Tocantins River basins.

Appearance:

• Slender, torpedo-shaped body with iridescent silver scales.

• Two distinct black spots on the body—one near the midsection and one near the tail.

• Bright red, orange, or yellow accents on the fins, depending on locality.

• Their “bucktooth” name comes from their sharp, small teeth, which they use to rip scales off other fish.

Size:

• Grows up to 5 inches (12 cm) in captivity.

Behavior & Temperament:

• Highly aggressive, especially in small numbers.

• Shoaling fish—must be kept in large groups (10+ fish) to prevent them from attacking each other.

• Known for scale-eating behavior—they nip at the scales of other fish, which makes them incompatible with most community fish.

• Constantly active, fast swimmers.

Tank Requirements:

• Tank Size: 75 gallons minimum for a small group (10+ fish); larger if keeping more.

• Water Parameters:

• Temperature: 74-82°F (23-28°C)

• pH: 5.5-7.5

• Hardness: Soft to moderately hard water

• Filtration: Strong filtration is needed due to their high activity levels.

• Aquascape:

• Open swimming space with some driftwood, rocks, and hardy plants.

• Avoid slow-growing plants as they may uproot them.

Diet:

• Carnivorous, but will eat some plant-based foods.

• Preferred foods:

• Live/Frozen: Bloodworms, brine shrimp, small fish, chopped seafood.

• Pellets/Flakes: High-protein pellets and flakes.

• Occasional Treats: Crickets, mealworms.

• Notorious for ignoring standard fish food in favor of live prey.

Tank Mates:

• Best kept in species-only tanks due to their aggression.

• If keeping with other fish, choose fast, aggressive species like:

• Large Cichlids (e.g., Jack Dempsey, Convict, Green Terror)

• Giant Danios

• Large Barbs (Tinfoil, Clown Barbs)

• Pike Cichlids

• Arowanas (if tank size allows)

• Avoid:

• Small, peaceful fish (they will be attacked)

• Slow-moving or long-finned species (they will be nipped)

• Bottom dwellers like Corydoras or Plecos (they might get harassed)

Breeding:

• Rarely bred in home aquariums due to their aggression.

• Egg scatterers that require soft, acidic water.

• Parents will eat their own eggs if not removed immediately.

Interesting Facts:

• Unlike most tetras, Exodon paradoxus is a scale-eater (lepidophagous) in the wild, feeding on the scales of other fish.

• Despite their aggression, they require large schools to feel safe—too few, and they will kill each other.

• One of the few tetras that can hold their own in predatory fish setups.