Black arowanas closely resemble the silver arowana in both shape and size. As juveniles, black arowanas have a distinct black band covering the length of their body.
However, as they mature, this band slowly disappears, leaving their body with a slight tint of purple, which is most prominent towards their anal fin (ooh la la).
Compared to the silver arowana, they grow considerably slower and also have a more slender body.
This arowana has an elongated body and a tapered tail. Once it reaches about 15 cm (0.5 ft), the markings disappear and the fish will develop a dark iridescent steel grey to blue coloration, hence its common name. Additionally, there are yellow and red outlining or the dorsal, caudal and tail fins. In contrast to the juveniles, adults are very similar to the silver arowana (O. bicirrhosum), but the two species can be separated by meristics.
Feeding and Nutrition of black arowana
Black Arowana are carnivores and are not picky; they should be provided with a variety of meaty and vitamin enriched foods such as live, frozen or freeze-dried ghost shrimp, krill, minnows, bloodworms, black worms, meal worms, earthworms, crickets, frogs, crayfish, and Cichlid/Arowana pellets or sticks.
Black Arowana require an aquarium of at least 240 gallons (300+ gallons with at least 30 inches in width is recommended) and should be provided with a sand or gravel substrate along with driftwood (the tannins in the driftwood will keep the pH lower to help simulate black water conditions) and vegetation.
They will also require an enclosed top (weighted down depending on the size of the specimen) on their aquarium as they are powerful and notorious jumpers. 25% water changes (RO water is recommended) should be carried out every 2 weeks (more or less frequently, depending on aquarium filtration efficiency).
Black Arowana aren’t overly aggressive (although they will hold their own and occasionally chase off other larger fish species), but can become very aggressive towards their own species. They will eat any live fish they can fit in their massive jaws (although they tend to refrain from eating plecos) and tank mates should be considered accordingly.