Diseases and Cures

In nature, all creatures are carriers of diseases to some extent. Some are infectious, while others are not. It depends on various factors and activities. Differences still exit between nature and in the aquarium, even though man may have artificially provided the best of conditions. An Arowana, like any other creature, can easily be infected once its resistance to disease is low.

Other than insufficient care, bacterial and parasitic contaminations are the main contributing factors when an Arowana is ill. The followings are brief descriptions of some diseases and their corresponding cures.

Condition and Treatments

Gill turning

Bad water quality, decaying leftovers, due to improper feeding and excessive excrement make the water quality bad, leading to high level of nitrate, ammonia, and decreasing the level of dissolved oxygen in the water.

Limited space:
When an Arowana is still growing, it needs sufficient space, together with proper nutritions. The length of the aquarium should be at least 3 times the length of the Arowana. Gills may be weak if swimming space is not sufficient.

In the early stage, gills cannot open and close smoothly with each breath. There are also signs of external tissue growth near the gills. The hard covers of the gill will tend to collapse, exposing the inside of the gills.

The condition will worsen if not treated. The Arowana will have difficulty in breathing; often raising it's head above the water to breathe. It will also soon stop eating, bacterial infection will set in, causing the gills to malfunction and the Arowana will die.

Incipient stage. When the Arowana breathes irregularly, change approximately 20% of the water every 2 to 3 days. Use air pumps and air stones to increase the level of dissolved oxygen in the water.

In the very serious stages, the gill tissues are totally sclerotic. An operation is necessary to have the infected portion removed.

Cloudy eye

a. Wounded cornea infected by tubular bacteria
b. Bad water quality or nitrogen in the fish's body

It usually happens to one of the eyes. At the beginning, the eye is mistily shaded. In later stages it's become blurred. In the end, the affected eye swells with white cotton-like cones growing outward. The Arowana can possibly die if no effective cure is applied.

When the eye is mistily shaded, change 1/3 of the water in the aquarium. Add some raw salt or sea-additive with a consistency of 5%. Keep the temperature at 30-33 degree C (86-91 degree F). Observe for two days, if it does not get worse, the only thing to do is to change 1/4 of the water every 3 days and adding raw salt until it heals. If there is worsening in condition, medication should be applied. Put in some soluble medication such as aureomycin, penicillin or other dedicated medication for fishes. Use the dedicated medication according to given instructions. When medications are in use, raise the temperature by 2-3 degree C and observe carefully.

It takes about 3-5 months for the Arowana to heal in the eyes. Gradually stop the usage of the medication if the eye does not swell anymore. The iris will look smaller after healing but functionally this is not a problem for the fish.

White spots (Ich)

White spots or Ich is very common in fishes. This disease is caused by a ciliate(Ichthyophthirius multifillis). Which reproduces very rapidly under the right condition. At 25 degree C one monocye can reproduce itself into more than 3000 individuals per hour. As the temperature goes up, it will slow in reproducing and eventually die.

Ich lives on the surface of the Arowana when it is low in resistance to diseases. It also absorbs the fish body fluid to reproduce and this is seen as the white powder-like cyst.

As the name suggests, at first white spots appear on the fins of an Arowana. Then it spreads all over the body. The Arowana will itch and rub itself against the wall or the bottom of the tank to stop the irritation. It will begin to lose its appetite and ulcers may form. Finally the gills don't function properly as the infection becomes heavy and finally can cause death. Prompt action should be taken once symptoms are observed to arrest further development of the disease.

a. Add some salt in the water consistency of 1%
b. Add 0.8 gram of quinone vitriol per 100 liters of

Raise the temperature 2-3 degree C higher after adding the medication of choice. Turn the air pump up to allow more dissolved oxygen in the water. Make sure Arowana obtains enough nutritions during treatment to strengthen the resistance to diseases. Be sure to disinfect the aquarium with potassium permanganate (KMnO4) when the Arowana recovers.

Warped scales

It is also called cone scales. Young Arowana are more easily infected than adult Arowana.

a. A sudden change in water temperature & change seasons
are possible causes.
b. Poor water quality

At the beginning, only few scales (5 to 8) are a little warped with congested roots. If attention is not immediate, the scales become bent and swollen. This raising of the scales will reduce the effectiveness on protecting the fish from invading pathogens like bacteria. The affected scales will finally drop off thus exposing an area on the body and increases the susceptibility of bacterial attack. This will result in ulceration and finally death in many cases.

Before the situation become worse, add a kilo of raw salt or sea-additive or refined salt in every 100 liters of water. Keep the temperature at 32-34 degree C (89-93 degree F). Change 1/4 of the water every 3 days. Warm the water with a heater before adding it into the aquarium. If the affected area is large, put some antibiotic in the water to prevent infection and other diseases.

Decay in Gills

Gill decay is caused by microscopic oval flagellate, not visible to the naked eye. It lives on the inside of the gill, absorbing nutrients for it's own division. Infection is especially dangerous at around 25 degree C as the rate of reproduction is very fast.

Bad water quality or a long interval between water changes.

The Arowana breathes heavily and gulps air. Body color fades away.

The same treatment as with white spots.

Water Mycosis

The fungus lives in the Arowana's wound, it has a light grayish coloration.

Cotton like fabric, which is the fungal, can be seen covering the wound. The Arowana becomes unstable when swimming and has a tendency to rub its body to stop itching. It can die from extreme physical weakness as a result of refusing to eat or due to secondary infection by bacteria agents.

a. Add some salt in the water to the consistency of 1%
b. Apply disinfectant to the wound or add 4-5 drops of
methyl red with a consistency of 5% in every 100
liters of water. Another alternative is the use of
malachite green but be very careful as this is poisonous
in higher doses than recommended.
c. Apply potassium chromatic solution of 1/30000 unit for 3
d. Use dedicated medication for fishes.


Ascites is usually found when the Arowana is young. Probably caused by decaying baits or by swallowing the pincers or fish bone, which could hurt the internal organs. Once this happens, wounds will be infected by vibrion and cause ascites.

At the beginning, the Arowana suffers from stomach flatulence; anal region becomes reddened and swells. When water cannot be expelled from the body, its swim bladder will be squeezed by the stomach. Thus, the Arowana cannot balance itself in the water with the head pointing down.

The ability to cure ascites is low. However, it is worth trying for an Arowana to take antibiotic or sulphonamide orally. Shorten the period between water changes and raise the temperature to 2-3 degree C.

Red spots

Also called red erysipelas, it is almost incurable in Arowana. It usually happens while the Arowana is young due to malfunctions of the filtering system.

The infection mostly happens near the tail. It begins with red dots. Later the infected areas swell and tend to warp. Finally the Arowana will die of ulceration as secondary infection sets in.

Try to raise the water temperature to 36 degree C (97 degree F). Give some antibiotic orally to your Arowana in addition to medication in the water. Do a 1/3 of water change daily adds raw salt or sea-additive of consistency of 5% and observe carefully.


Living baits used to feed Arowana are the usual parasite carriers. Other common external parasites are fish louse and anchor worm.

Fish louse (Argulus Spp.)
Fish louse is from the crustacean family. The body is about 3-5 mm in length with flat shell, thus it can be seen with the bare eye. It attaches itself to the fish via a sucking device, the oculus. Its has needle like structures that anchors onto the Arowana body and withdraw the body fluid of the fish, making the body less lustrous. The Arowana will rub their body against the tank walls to get rid of the irritation caused by the fish louse.

Anchor Worm
It lives on the fins or in partially embedded into the fish body. Spike about 1 cm long, grows on it's head which are used to absorb nutrition directly from the Arowana's body. The infected area swells and becomes ulcerated. An infected Arowana becomes impatient with less appetite and begins rubbing its body in a bid to get rid of the parasite.

Disinfect with organic phosphoric acid of 1/5000 000 consistency or use 2 grams of potassium permanganate (KmnO4) in every 2 liters of water. Fish louse will also fall off after the Arowana is pit in higher consistency salt water for 3 minutes. Be sure to allow enough oxygen in the water. For anchor worm use san-Iv-song solution at 1/1000 000 consistency (equivalent to 1 gram per 100 L). Or use formalin instead, put 5 ml in every 100 liters of water to kill the Parasites.

Note: Be sure to disinfect the aquarium when the Arowana heals.

Generally, adding salt in the water and raising the water's temperature are the safest cure with no side effect. Medicine is only used as the last remedy. When you have to do so, apply half of the dosage of the normal amount first. Then increase or decrease the amount according to the state of illness to avoid resistance to the drugs building up in the Arowana's body.