Silver arowana (Osteoglossum bicirrhosum)
Silver arowana or Dragon Fish (Osteoglossum bicirrhosum) is a tropical freshwater fish of Osteoglossidae family. It’s a popular tank fish, which is often kept in zoos, public and amateur tanks around the world.
Inhabitance in the wild
The fish is native to South America river basins – such as the Amazon river, Rupununi, Orinoco and Essequibo river. The fish was introduced in North America, several times arowana was caught in USA, in ponds of different states. Dragon fish inhabits in backwaters and inshore zones of rivers and lakes with water temperature about +24…+30 °C. Each year during overflow of the Amazon river this fish swims into flooded bottomland forests. Silver arowana can live in oxygen-deficient waters.
The fish body may be up to 90 cm (35 in) long, more seldom – up to 120 cm (47 in). It’s weight is up to 6 kg (13 lb), in average usually it’s 4.6 kg (10 lb). Its tape-like body is rather flattened from sides, covered in very pale scales with some silvery glitter and golden tint. Young arowana fish body has yellow-orange stripes and some blueish glitter on it. The fish dorsal and anal fins are very long and narrow-width, they almost coalesce with its fluke. Together with very wide and flattened laterally tail-stem of the fish they form an unusual “paddle” which gives arowana rather strong acceleration when the fish attacks its prey and it allows the fish to jump out from water quite high to catch something. Once a scared arowana in a tank jumped out of it 3 meters high.
Arowana dorsal has about 42-50 rays and 49-58 rays in the anal one. Arowana’s body has 30-37 scales on its lateral line and it has 84-92 spinal bones. The fish has very wide upward-pointing mouth and there are 2 fleshy barbels on the edge of its mandible. Most of the time Silver arowana slowly swims close to water surface, at that its barbels are pointed forward and it looks like the fish is probing water by doing this.
Difficulties in keeping
This tank fish is definitely not for the beginners. Even young silver arowana fish requires a spacious tank, since it grows rather fast. A tank of 250 liters (66 gallons) is enough for young species, however rather quickly the fish will require a bigger tank, about 800–1000 liters (265 gallons). Also the fish needs very clean and fresh water. However, arowana, just like the majority of freshwater fish, is rather tolerant to changes of water pH and hardness. Besides, to feed arowana isn’t a cheap thing.
Keeping in a tank
The most important condition to be observed to keep this fish in a tank is the size of this tank. Recommended tank capacity must be over 500 liters (132 gallons). Minimal tank size is 160 cm long, 60 cm wide and 50 cm high. Ideal tank size for Silver arowana has to satisfy the following formula: the tank length has to be at least 3 times larger than the fish length and the tank width should be not less than 1.2 of the fish size.
It’s acceptable to keep young silver arowana in smaller tanks temporary, however, later the fish must be taken into a proper sized tank to avoid the fish body deformation and to insure the fish maximum life span and body length. The tank has to be securely closed with some glass from the top to prevent the fish from jumping out of it.
Silver arowana prefers soft water with pH value from 6.0 up to neutral. The fish requires strong water filtration, 25-30% of water, and weekly tank cleaning to keep the proper water characteristics. Tank water temperature should be from 24 to 28° С (75-82F), ideally it should be close to 26°С(78F).
|Scientific Name||Osteoglossum bicirrhosum|
|Common Name||Silver Arowana, Dragon Fish, Arawana, Monkey fish|
|Tank size||250 liters (66 gallons) and more|
|Temperament||Peaceful towards fish of similar size|
|Temperature||24 to 28° С (75-82F)|
|Size||120 cm (47 in)|
Dragon fish hunts mainly close to water surface. It is an omnivorous fish, but it feeds mainly on fish, though it eagerly catches large insects (mostly bugs), spiders, crabs, snails, frogs and other small selva inhabitants, including terrain and tree dwelling ones, which sit on the branches and leaves hanging above the water and arowana jumps out of the water to get them. It is said that even snakes and birds were found in arowanas stomachs as well as some plant remnants, which speaks for the fact, that the fish really is an omnivorous one.
In the wild arowanas eat food with huge amount of bulk substance – such as bird feathers, insects chitin etc. It means that you should feed the fish in a tank correspondingly to all above mentioned. The fish diet may include large insects, shrimps, fish (not more than twice a week), large arowana species may be fed with small animals, for example, mice. You may also use some special food made for arowana. You mustn’t feed the fish with food that drowns all the time, since it may cause the fish eye focus shifting (cross-eye). Large amount of fat food also may cause the same disease, because too much fat leads to relaxation of skin structure under the disease eye. In the wild eyes of healthy fish are directed vertically, not downwards.
Frogs are favorite food of many arowana species. They may get used to it that much, that they’ll stop eating any other feed. You can buy frogs in a pet shop or on the market.
Feeding arowana with live small fishes will let you observe the process of arowana hunting, so it’s not only just some nutritive food for the fish. Such fish should be selected according to the size, so arowana would easily swallow them. It shouldn’t be a gorefish and it shouldn’t have any sharp poisonous pins. Another rule – this must be tank fish without any infectious diseases.
When buying silver arowana to keep it in your tank, keep in mind that this is a predator fish. However, it does well with other tank mates, if they are 3 times larger than it is. There should be not more than one adult arowana in a tank, since this fish tends to be aggressive to the species of its kind. Silver arowana can be kept together with other middle-sized tank fish (green terror, black ghost knifefish, cichlid parrot fish, large botia fish, saifin pleco, freshwater angelfish).
The fish doesn’t breed in captivity. Therefore, the fish is bread in fish farms of South-East Asia using hormones. The fish breeds at the beginning of flood. Arowana female lays a small number of eggs, which is carried by the male fish in its mouth. According to the observations in captivity arowana male fish incubates the eggs for 40 days. The eggs are very large, red-orange, drop-shaped with high amount of nutrient substances. Arowana juveniles hatch being 3 cm large, after that they continue staying in one of their parents’ mouths and they swim out from time to time. Their yolk sac continues to be the source of food for juveniles which are 6-7 cm long. Young arowana fish leaves its parents’ mouth 5 weeks later since the day it hatched. After the juveniles yolk sac comes to an end, they start eating the feed you give them.