Whiptail Rivulus Tetra

Tetragonopterus argenteus is a medium-sized, hardy schooling characin from the Amazon basin with a robust, deep-bodied build and a characteristic dark spot at the base of the caudal peduncle. It is a widespread, adaptable species found across a broad range of Amazon habitats and is tolerant of a reasonably wide range of water parameters compared to many specialist SA tetras. Growing to about 12 cm, it is larger than most tetra species typically encountered in the hobby.

In the aquarium Tetragonopterus argenteus requires a minimum 150-litre setup with good filtration, soft to moderately hard water, and plenty of open mid-water swimming space. It is an active, energetic schooling fish that in groups of eight or more creates an impressive display in a large South American community aquarium. It is somewhat boisterous and may fin-nip in small numbers, but large schools with matched-size tankmates prevent this.

Feeding is straightforward — it accepts pellets, flakes, frozen bloodworm, and brine shrimp readily. Tetragonopterus argenteus is compatible with other medium to large SA species including large geophagine cichlids, larger catfish, and medium tetras. Its combination of hardiness, attractive caudal spot, and active schooling behaviour make it a practical choice for aquarists building large South American community displays.

Water: Soft to moderately hard, pH 5.5–7.5, 23–28°C; adaptable; regular water changes. Tank: 150 L minimum; open mid-water; group of 8+ to suppress fin-nipping. Feeding: Omnivore — pellets, flake, frozen bloodworm, brine shrimp; accepts most foods. Breeding: Egg-scatterer; possible in soft water with fine-leaved plants. Compatibility: Peaceful in large groups; good with medium-large SA community fish.