Silver Arowana

The silver arowana (Osteoglossum bicirrhosum) is a South American surface predator native to the Amazon drainage and the Orinoco, Rupununi and Essequibo systems of the Guianas, living in both whitewater and blackwater floodplains. It is abundant in flooded areas, is IUCN Least Concern and is not on any CITES appendix - which makes it the legal, widely available alternative to the Asian arowana. Males mouthbrood the eggs and early juveniles for about two months.

Adults reach 90-100 cm, with credible reports to 1.2 m, so the profile's 90 cm is the floor of the adult range, not the ceiling. In human care they have lived beyond 10 years. Size the enclosure for a 1 m+ fish from the start - the long, laterally compressed body needs length far more than height.

The silver arowana is the 'water monkey' of the Amazon: it waits just under the surface, then launches out of the water to grab prey, hiding parallel to a downed tree before it strikes. It is a powerful, nervous fish that will crash into the glass or clear an open lid when startled, so drape the sides, cover the top and avoid sudden movement or tapping near the tank. In practice it is a solitary surface cruiser rather than a shoaling or bottom-dwelling fish. Confidence note: medium-confidence guidance drawn from published species care information; treat as conservative guidance, not a precise requirement.

Adults reach around 90-100 cm and need a footprint of at least 1,500 litres with a wide, well-covered top, since they routinely jump. A tight, weighted lid is essential: startled fish crash into glass or leap clean out of an open tank, and they can jump over a metre out of the water to snatch insects. Keep the water clean, give it heavy filtration, and leave the surface lane unobstructed for hunting. Confidence note: medium-confidence guidance drawn from published species care information; treat as conservative guidance, not a precise requirement.

Judge the tank by usable floor length and width, not by litres: a laterally compressed 1 m surface cruiser needs a long, wide box (on the order of 2.5 x 1 m of floor) and gains nothing from height. A 500 L tank can match the volume of a wide 1,500 L footprint only by being tall and narrow, which is exactly the wrong shape for this fish. Keep the full length of the surface open as a hunting lane. Confidence note: medium-confidence guidance drawn from published species care information; treat as conservative guidance, not a precise requirement.

Surface-oriented predator with an omnivore label but an overwhelmingly meaty diet: wild fish take snails, crustaceans such as crabs, insects, spiders and smaller fish, plus occasional birds, bats, mice and snakes. Its drawbridge mouth is built to snatch items off the surface, so present floating or surface-held foods. Feed a varied meaty diet - do not read 'omnivore' as licence to make plant matter a staple. Confidence note: medium-confidence guidance drawn from published species care information; treat as conservative guidance, not a precise requirement.

Anything that fits in its mouth is food - they will eat any tankmate that fits in their mouth - and bottom-dwellers do not automatically escape conflict despite hunting at the surface. In practice this means species-only housing, or tankmates far too large to swallow in a very large tank. Invertebrates such as crabs and snails are prey, not cleanup crew. Confidence note: medium-confidence guidance drawn from published species care information; treat as conservative guidance, not a precise requirement.

Verdict: a spectacular but demanding pet fish - plan 1,500+ litres, a weighted tight lid and heavy filtration from day one. It is jump-prone, nervous and predatory, so an open lid and small tankmates are exactly how people lose them. It is legal and common (IUCN Least Concern, not CITES-listed), which makes it the sensible arowana for experienced keepers with the floor space - and a bad first fish for anyone. Confidence note: medium-confidence guidance drawn from published species care information; treat as conservative guidance, not a precise requirement.