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Hiroshi Azuma
Breeding the Gold Asian Arowana in an Aquarium Tank
Summary: Likely the first recorded breeding of the Asian Arowana Scleropages formosus in a home aquarium.
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#205 - 5525 West Boulevard
Vancouver, British Columbia
V6M 3W6

Breeding the Gold Asian Arowana in an Aquarium Tank

Hiroshi Azuma - all photos by author


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Captive bred Asian Gold Arowana - 9 inches long, 7 months old

This article is the culmination of nearly two decades of effort: a captive-bred gold Asian arowana, seen in the photo above.


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Hiroshi Azumi at work in lab

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The author's impressive setup for observing his fishes includes remote video monitoring

For many years I have been attempting to breed the Asian Arowana, Scleropages formosus. This rare and highly prized fish hails from southeastern Thailand, Borneo, and Sumatra, where it is increasingly endangered by over fishing and habitat loss. It must be stressed that trade in this species is strictly controlled by CITES and other regulatory agencies, and possessing them requires a lot of permits and paperwork. Arowana belong to a group of primitive fishes known as bonytongues and in fact the bony tongue of the  dried specimen in the photo below is clearly visible. Curios such as this are sold in Thailand and other areas of the Far East, and may be counted as part of the reason this species is endangered.

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A dried Arowana specimen - note the bony tounge

I began to research and formulate a breeding plan in 1972; at that time I thought that if everything went according to plan I would be successful within 5 to 6 years. Was I ever wrong!

I first spawned the species in 1974, in a 180-gallon tank with dimensions of 72" X 24" X 24". Unfortunately, the eggs disappeared. I do not know if they were fertile or not. In 1976, I tried again. I was able to coerce six well-conditioned pairs of the fish into spawning, but again none of the eggs hatched. Virtually every year since the fish spawned, but no successful breeding resulted. Several times I tried hatching the eggs artificially, without success.

After the sixth year of unsuccessful Arowana spawns, I was getting pretty discouraged. My wife kept encouraging me, however. She has always been a great help to me in my fish breeding efforts, from beginning to end. Though she is busy, she still takes great interest in fish behavior and helps me tend the tanks. All in all, I observed some 30 spawns between 1974 and 1989, all to no avail.

Thinking that maybe tank size was the problem, in 1980 I set up a very large spawning tank160" X 34" X 24". In 1984 I set up two additional large tanks, each measuring 120" X 34" X 32". In both cases the fish spawned as usual, but again their eggs failed to hatch. Each spawn consisted of 30-80 eggs, averaging 40. The male would begin to brood the eggs in his mouth, carrying them for 10-20 days, but afterwards would eat his eggs. The eggs appeared to be very delicate, and as I've already mentioned, attempts to incubate them artificially failed. All in all, I observed some 30 spawns between 1974 and 1989, all to no avail. I was ready to give up. One day, yet another pair of my gold Arowana spawned. I was not even terribly interested, thinking that again the eggs would be lost. But this time was different-----the male was brooding perfectly. At last, success! November 4, 1989, was a day I will always remember, for that was the day when the Arowana spawned what would become their first brood to be brought to term. Let me describe my setup in detail. In August, 1989, I set up a the tank measuring 60" X 30" X 18", with a volume of about 140 gallons. It was filtered by a large external filter l constructed myself; the filter box was 18" X 8" X 8", and was powered by a water pump moving about 260 gal/hr.


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   A subtle means of sexing S. formosus is in the mouth-the male's is wider and
deeper. In this photo, the specimen with the tongue visible is a male.

The tank was in a basement room and received only artificial light. Two 40-watt fluorescent tubes lit the tank for 14 hours a day, and a 5-watt night light was left on 24 hours a day. A 300-watt heater was used. The tank had no gravel, but there was floating water sprite, Ceratopteris thalictroides at the surface. The pH was maintained at 5.6-6.1, and the temperature at 84-86F.

Not wanting to disturb the fish unduly, I generally did not enter their room except for feeding and water changes. The rest of the time, I observed them via video monitors, recording important activity on a VCR. I also took still photos with a remote-controlled 35 mm camera.

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  Preserved Arowana eggs - I examined these, and virtually every other physical and biological
factor that could be examined in an effort to explain the breeding failures of my fish

Into this tank I placed an adult pair of gold Asian Arowanas. The male was a bit over nine years old and was about 22 inches long. The female was a seven-year-old, 20 inch specimen. They were the only inhabitants of their tank except for a few small dither fish. I fed the pair live goldfish, dry food sticks, freeze-dried krill, and occasional live crawfish. I changed one-third of the tank water at least every two weeks, and at times even every week when I felt it necessary.

The fish shortly began to show pre-spawning behavior. By day they swam in slow circles around the perimeter of the tank, the male trailing the female; by night they still swam in circles, but at high speed. This courtship continued for 2-3 months. To use another mouthbrooding fish as a contrast, in Tilapia mossambica courtship usually lasts only 1-3 days, and can even be as short as 30 minutes!

In October the fish were clearly getting more excited. They began swimming a bit faster all the time, and in tighter circles. At this point they were feeding very heavily, and I added live shrimp, grasshoppers, and crickets to the diet already outlined. Because they were eating so much, I increased the water changes to weekly. The tank temperature was 83-84F and the pH ranged between 5.2 and 5.8.

Around the 24th of October, there was another change in the pair's behavior. The male stopped following behind the female and now the fish swam slowly side-by-side. In addition, their circling occupied only half of the aquarium. Sometimes, the male would bite at the female's caudal, anal, or pectoral fins, and these became a bit tattered. I was worried that the male would injure or kill the female. However, she did not attempt to retreat from the male, and in fact the pair bonding seemed to strengthen, with lots of rubbing and other body contact.

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A fresh Arowana egg. The eggs are about one-third inch in diameter, and approximately 4060 are laid in
one spawning effort. Infertile eggs may be consumed by the male while brooding, and could provide
supplemental nourishment to sustain him while he is unable to obtain food externally.

The appetites of both fish dropped markedly, though they would occasionally eat a few grasshoppers or crickets from the surface. The water temperature was 82F; pH, 6.1-6.4. For the time being, I stopped the water changes.

On November 4th, from about 7:00 AM to 12:00 PM, the fish moved in very slow, very tight circles occupying only about 16 inches of the tank's length. The female kept to the tile outside of the circle, and would sometimes remain motionless as the male continued circling. Occasionally the fish would both be stationary, rubbing against each other. The water temperature was 84; pH, 6.1. I performed no water changes and did not offer any food.

Finally, just a little after noon, the fish stopped swimming around and lay quietly just above the bottom, rubbing gently against each other. Then, quite suddenly, they spawned. With a spasm, the female released a cluster of eggs, which the male simultaneously fertilized with a near-invisible cloud of sperm. Immediately the male began to scoop the eggs into his mouth. With a very soft touch, he picked them up one by one. After spawning, the male and female swam together all the time.

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The mate Arowana, seen about a week offer spawning, with gular pouch expanded with eggs.

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The male's buccal cavity continued to expand. This is the view some five weeks after spawning.

The female ate a few eggs, but the male did not swallow a single one; his mouth was very swollen with his brood. Here are a few particulars on the eggs. There were 40-60 of them, each with a diameter of 15-18 mm (nearly three-quarters of an inch). The eggs were orange-red in color, non-adhesive, and sank to the bottom. The eggs were very soft and their membranes very thin. After spawning, the male and female swam together all the time. When viewed from the front, the male showed twin oval black markings on his lower jaw; I call these "brooding marks." The female swam slightly above the male, with her pectoral fins spread horizontally, like an honor guard. I call this the "guardian pose." These two post-spawning behaviors are especially noteworthy, I think.

I offered goldfish, which the male (thankfully!) did not eat, but the female took a few on the fifth day after spawning. On November 16th, twelve days after spawning, I believed that perhaps the eggs had begun hatching, because I found an empty eggshell on the bottom of the tank. The fish were still sticking together inseparably. On November 26th, I decided to remove the female. The pair were still behaving compatibly, but the female had begun eating goldfish voraciously, and water conditions had begun to suffer from the amount of waste she was producing. The pH had dropped to about 5.2-5.6. I did not want to do a water change for fear that altering water conditions rapidly would harm the eggs or fry.

By the 20th of December the male had still not released any fry, but his mouth was very swollen. He had not taken any food since the day before spawning ...or had he? I noted that the male was still excreting some fecal material, and this was the same color as the eggs.


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The twin black patches on the lower jaw of the brooding male, which I called "brooding marks."


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The brooding male often rested in the thicket of floating plants.


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This view is somewhat blurred, as it was shot from a video monitor,
but shows fry swimming outside their father's mouth.


I surmised that the male was eating the non-viable eggs from the clutch he was brooding. At this point the tank water had a pH of 6.2-6.4, and the temperature was running 83-86F. I became bold enough to start doing water changes again, about one-fifth every 1-2 weeks.

December 23rd was the day I had waited for. At last the fry began to leave their father's mouth for short periods. If they felt threatened, they would immediately return to this safe refuge. Additionally, the fry would always return to their father's mouth at night. The male's activity at this time was somewhat sluggish-he would swim very slowly about, or rest motionless on the bottom or at the surface. By night he was a little more active, and would roam a larger portion of the tank. The floating plants seemed to be preferred as resting places by both the father and the fry. The adult still took no food.

On the 3rd of January, 1990, about 60 days after spawning, the fry finally swam free of their father for extended periods of time; while they still hung close to his mouth, they did not attempt to return to it. Their yolk sacs were very small. I counted 21 fry in all. Three days later, I removed the male to a separate tank, but it was another 10 days before he took floating dry food, and two weeks before he began feeding on live goldfish.


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The eye of one of the fry can be seen inside the male's mouth


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The spawning yielded 21 fry, about half the number of eggs that had been spawned.


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One of the fry soon after release, measuring just over 3 inches.

On January 8th the Arowana fry began feeding on live bloodworms, and a day later they accepted live white clouds. The active small fish really seemed to stimulate the young Arowanas. The fry began to fight among themselves, so I removed each one to its own 10-gallon tank, keeping them at a pH of 6.2-6.4, and a temperature of 82-84F. When setting up these individual tanks, half of the water was taken from the spawning tank, and half was new water. In the fry rearing tanks, I changed one-quarter to one-third of the water every 1-2 weeks. The fry grew at an incredible rate. At 60 days (post-spawning) they were about 3 inches long; at 120 days they were up to 5.6 inches; at 180 days, 7.2 inches; and at 210 days the largest fry were just under 9 inches long.

I believe that the natural breeding cycle for Scleropages formosus is only once a year, but often, young females (4-7 years old) will spawn twice a year.

Spawning the Asian Arowana was the realization of a dream spanning nearly 20 years. This fish certainly has little commercial potential, and of course the number of hobbyists keeping this species will always be limited because of its endangered status, but for the lucky hobbyists and public aquaria that can obtain the proper permits, this beautiful fish presents an unprecedented challenge.

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This placid photo of happy fry belies their true nature. In reality, they are quite territorial and pugnacious with each other, and the author was forced to give each one its own 10-gallon tank. Small yolk sacs are still visible through the abdominal walls of these fry, though they were also feeding heavily on live bloodworms.

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An Arowana fry at a little over 5 inches and 3.5 months of age. At this
point they were feeding well on live white clouds.

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By five months of age it was obvious that the fish were developing nice golden coloration,
like their parents. The Asian Arowana is rare enough, but the gold, orange, and red color morphs
of the species are especially scarce and thus highly prized.