The Silver Arowana (Osteoglossum bicirrhosum) is a long and beautiful fish known for its voracious appetite and constant surface skimming, looking for things to fit into its mouth. It is native to waterways of the Amazon River and other areas in South America.
It is a very popular fish for intermediate to expert aquarists as it swims fairly gracefully and with purpose and has a nice and powerful jaw. Aquarists like to watch it feed, especially live foods such as earthworms and other insects. A true carnivore, the silver arowana can be aggressive, especially toward smaller fish in the tank, so if you are going to keep an arowana with other fish, choose tankmates wisely. Fish that inhabit the middle and lower portion of the aquarium’s water column are preferable.
The silver arowana’s domain is near the surface, where it stays most of the time. The silver arowana is a visual hunter, and it has been observed in the wild jumping out of the water to snatch a hapless bug from an overhanging tree branch.
The silver arowana is not a beginner fish, but is more suitable for intermediate to advanced aquarists. It requires a large aquarium with strong filtration and a diet of primarily live foods such as feeder fish, earthworms and other insects. It will also eat floating foodsticks.
With proper care, the silver arowana is a very hardy fish. It can have issues such as gill curl, which is often due to bad water quality and limited space to move about; white spot (ich), cloudy eyes, and coned scales are the other arowana ailments. Common cures can remedy these conditions.
The silver arowana can grow to more than 3 feet in length. It has an elongated body, almost knifelike in look, with a compact and wedge-shaped head. It has a wide, underhang jaw that opens like a trapdoor whenever it feeds. It has large scales and two barbels hanging from the tip of its jaw, hence the scientific name bicirrhosum, which means “two barbels.” The barbels are sensory organs, able to detect movement on the water’s surface.
The fish is found in the Amazon Basin, with related species such as the Asian arowana found in Asia, and an Australian species. It resides primarily in slow-moving rivers and waters that flow into swamps and wetlands.
The silver arowana is best kept in large aquariums with tankmates that are just as large or too big to fit into its mouth. The silver arowana can share space with larger fish that inhabit the lower strata of the aquarium, such as clown knifefish, large plecostomus, oscars and other large cichlids. The silver arowana can also live alone or in groups of three. The Australian arowana is best kept alone in its own aquarium. Due to its physiology and natural habits, a long tank is desired over a tall one, with recommendations of the aquarium measurements equal to three times the length of the arowana. A minimum tank size of 72 by 30 by 24 inches is ideal. Two hundred gallons is the generally accepted minimum capacity. Ideal water conditions are pH of 6.0 to 7.5 and a water temperature range of 75-83 degrees Farenheit.
The silver arowana requires a long, rectangular aquarium with a lot of surface area to patrol as it spends most of its time swimming back and forth on the surface looking for food. A lid is also required as the arowana is a very accomplished jumper. Because it eats so much, the silver arowana produces a lot of waste material, so frequent water changes are a must. Bi-weekly water changes of 20 to 25 percent are ideal. Pay special attention to water conditions and test for ammonia, nitrate and nitrites regularly.
Most silver arowana in captivity are bred on fish farms. The fish is a mouthbrooder, with the male doing the babysitting for three weeks until the fry reach a size of around 3-4 centimeters, where they can then hunt on their own, returning to the male only when danger arises. At approximately five weeks, they leave the male for good.