Origin
Osteoglossum ferreirai inhabits the Rio Negro tributaries of the Amazon. The water there is extremely soft (TDS under 50), acidic (pH 4.5–6.0), and stained brown by tannins from leaf litter.
Captive black arowanas adapt to a wider range, but they remain sensitive to mineral hardness and pH swings.
Juvenile vs Adult Appearance
Juvenile black arowanas under 12 inches display a striking yellow-orange lateral band against jet-black body and fins. This is the trait that drives their popularity in the trade.
As they mature past 12 inches, the bright juvenile coloration fades to a muted dark gray with subtle blue-green iridescence. Adult black arowanas look similar to dull silvers — many keepers are disappointed by this transition.
Tank Requirements
Same physical requirements as silver arowanas: 250+ gallons adult, 8-foot length, weighted lid. Add: blackwater conditions if possible (Indian almond leaves, peat moss, dim lighting).
A wet/dry sump is ideal for maintaining stable parameters in soft, acidic water.
Health Sensitivities
Black arowanas are more prone to ich, holes-in-the-head, and bacterial infections than silvers. They do not tolerate sudden water changes well.
Acclimate slowly. Drip-acclimate for 2+ hours. Match temperature precisely. Black arowanas can die from a 2°F shock that a silver would shrug off.