Minimum Tank Size: 250 Gallons (946 Liters)
Care Level: Very Difficult
Water Conditions: 6.0-7.0 pH and Soft to Moderately Hard
Temperature: 75-82° F (24-27° C)
Maximum Size: 36 inches (91.5 centimeters)
The silver arowana (Osteoglossum bicirrhosum) is easily one of the most iconic fish in the aquarium hobby, even if the average aquarist could never hope to keep one. Nearly everyone has seen one of these beautiful fish at a pet store, and dreamed of the day they could afford what amounts to a small indoor pool in order to house one of these fish.
These fish are known by several names, and many aquarists refer to them to as dragon fish, because of their shiny scales, and double barbels on their chins, that make them resemble mythological Asian dragons. They are also sometimes known as monkey fish, due to their ability to leap out of the water and capture prey on low hanging branches.
And if multiple names weren’t confusing enough, they are also known by alternate spellings of arowana, which include arahuana, and arawana.
Silver arowanas are native to South America and are found in Brazil, Guyana, Colombia and French Guiana. They inhabit the Amazon basin, and the Rupununi and Oyapock Rivers, although they can also be found seasonally in other bodies of water.
In recent years, invasive populations have become established in Florida and Thailand through aquarium releases. However, at this time there doesn’t appear to be any restrictions on keeping these fish, although anyone looking to purchase one should always check with local authorities to ensure there are no regulations.
These fish can live up for 20 years in a home aquarium, and the purchase of a silver arowana should never be taken lightly. Their long life, combined with their tank busting size, makes them a fish only the most experienced aquarists should tackle.
One of the odd discrepancies in the literature about silver arowanas is that their listed maximum size varies wildly. Most of the more respected publications state the maximum size to be between 30 and 36 inches (76-91.5 cm) although some publications peg it as high as 48 inches (122 cm) or as low as 24 inches (61 cm). Why there is so much disagreement over the maximum size is unknown, but through personal experience I can state most arowanas kept in captivity grow to about 36 inches (91.5cm) in length.
For a silver arowana to be healthy in captivity, they have to be housed in the largest aquariums on the market. The bare minimum tank size for a single silver arowana is 250 gallons, and if anything less is provided, it’s almost guaranteed issues will arise. These fish should only be kept together as juveniles, unless the intention is to keep them in a large, natural pond (or a custom aquarium of similar size).
One of the most difficult problems to overcome with smaller tank sizes, is that silver arowanas are noted jumpers. It is believed that if these fish feel their tank is too small, they will repeatedly attempt to leap to freedom.
If their tank isn’t covered, then their attempted escapes will usually result in a dead fish (although they can breathe out of water for short periods of time). And if their tank is covered, they may eventually severely injure themselves as they repeated propel themselves into the cover. So it’s best to only tackle these fish if a person can provide them with an appropriately sized tank.
And it can’t be stressed enough that their fish tanks MUST be covered. These are fish that can leap up and snatch birds from tree branches, and that combined with the fact that they can be skittish when first introduced to a tank, usually results in them almost immediately leaping out of an uncovered tank.
It can be difficult choosing tank mates for silver arowanas, since for such a large fish, they are surprisingly susceptible to bullying from aggressive fish. And smaller, more docile fish aren’t an option either, since most of them usually end up in the silver arowana’s drawbridge like mouth.
But there are some tank mates that usually work, and I stress the word usually. These include similarly sized plecos, catfish, bichirs, and some of the less aggressive cichlids, like jurupari (eartheater) cichlids. Although it should be noted that the temperament of fish can vary from individual to individual, so always have a backup plan in case aggression issues arise after adding a new fish.
Any tank containing silver arowanas should have a substrate of small grain gravel, or aquarium safe sand. It should also be lightly planted, and since these fish are almost always in motion, large swimming areas must be kept clear.
A canister filter is almost always the best choice for a silver arowana tank, simply because they are the only filter that can truly handle the massive tank sizes needed. While tandem hang-on-back filters may work, they are far from ideal in most instances.
In the wild, these fish are a menace to anything above, on, or below the water surface. They have been known to eat snakes, birds, mice, and even bats, but their preferred diet is mainly aquatic. These fish primarily feed on crustaceans, fish, and insects, and this diet should be replicated as closely as possible in the home aquarium.
Some silver arowana can be trained to take fish food pellets, but most will prefer a very meaty diet, with the regular addition of feeder fish. Some of the best foods to feed them are earthworms (be careful they aren’t taken from areas where pesticides are used), shrimp, beef heart, and crab meat.
They will also take any of the frozen fish foods, which include blood worms, daphnia, and brine shrimp, but this is generally only worthwhile when they are juveniles. As they grow, they will need to eat vast quantities of these, and the price would quickly become prohibitive.
A person should at least attempt to train a silver arowana to eat prepared fish foods, since this helps to ensure they have a balanced diet. This can often be accomplished by mixing the prepared foods in with their other food stuffs, until they learn to take the fish food on its own. One of the best choices is Hikari Carnisticks Sticks, which are perfect for large carnivores like the silver arowana.
While feeder fish are relished by silver arowanas, they come with their own set of problems. Any responsible aquarist wouldn’t touch the feeder fish available at pet stores with a 10 foot pole. They are often disease and parasite ridden, and adding them to an aquarium also adds their illnesses to the water.
If a person is dead set on using feeder fish, they should start breeding them on their own to ensure they are completely healthy. The very best feeder fish are rosy red minnows, and they are both nutritious, and fast breeders. You can learn how to breed rosy red minnows here.
There are few recorded instances of silver arowanas breeding in a home aquarium, and most are bred in large, natural ponds. If an aquarist wants to attempt breeding them, they should be purchased as juveniles and allowed to pair off. It should be noted that the few people claiming to have had success usually had tanks well in excess of 500 gallons – something few aquarists can afford, and ever fewer house floors can support.
These fish are egg layers and care for their brood. In the wild, they pair off at the beginning of the rainy season, and build a nest where the female lays her eggs. After the eggs have been laid, the male will take the eggs into his mouth and care for the fry for the next 50-60 days.