Origin and Wild Behavior
Silver arowanas (Osteoglossum bicirrhosum) inhabit the Amazon and Essequibo basins of South America. They are surface ambush predators specialized in hunting insects, bats, small birds, and fish that fall or swim near the water surface.
In the wild, they reach 4 feet and live in flooded forest channels. Captive specimens commonly reach 30–36 inches in 5 years given adequate space and diet.
Tank Requirements
A juvenile silver arowana under 8 inches can live in a 75-gallon tank for 6 months. By 12 inches, you need 180+ gallons. By adult size, 300+ gallons is the minimum, with 8-foot length essential.
Use a tightly weighted lid. Silver arowanas are the most powerful jumpers in the genus — they routinely launch 18 inches out of the water to grab prey. Standard hinged lids are insufficient.
Diet and Feeding
Juvenile silvers prefer live insects: crickets, mealworms, earthworms. Transition them to floating pellets early to avoid feeder dependence. Adults thrive on a mixed diet of pellets, frozen krill, prawns, and the occasional cricket.
Feed juveniles twice daily, adults every other day. Overfeeding leads to fatty liver disease — a leading cause of premature death in captive silvers.
Common Health Issues
Silvers are prone to ich during temperature drops, fin rot from poor water quality, and the dreaded drop eye from improper tank setup. Watch for "head-down" posture, which signals swim bladder issues from cold water or constipation.
Internal parasites are common in wild-caught specimens. A prophylactic Praziquantel treatment after acclimation is wise.
Color and Growth
Healthy silvers display iridescent silver-blue scales with subtle pink and gold sheen along the body. Color intensity depends on diet (carotenoid-rich foods like krill help), water quality, and lighting (subdued lighting deepens iridescence).
Growth rate: roughly 2–3 inches per month for the first year, then slowing to 1 inch per month, then 2–3 inches per year after age 3.