Jeremy Gay advises on the best way to keep these large but popular aquarium fish.
Of the three valid Scleropages species, S. leichardti is the least common. The Pearl arowana, S. jardini, is popular, though with greater availability of captive-raised S. formosus coming from Singapore fish farms, those who know their arowana and have the financial means are prefering these trophy dragonfish.
S. formosus happens to be shorter in adult length, more colorful and less aggressive than the Australian pearl arowana, S. jardini.
Captive care
Having visited many farms in Singapore, we advise the best way to ensure happy fish is to keep them in a huge tropical pond. The combination of swimming space, coloured water, natural sunlight and natural foods suits them, and all the world’s best arowana are raised in mud ponds to condition them prior to being shown.
We noticed a significant decline in quality and condition of fish held long term in aquaria, with loss of colour, marks from collision injuries and increasing numbers of fish with the condition drop eye.
We reckon that once you have seen a pair of Super red or Golden crossback arowana gliding at the surface of a sunlit 9m/30’ tropical pond, you may decide not to keep them in aquaria at all.
However, we are also well aware of budgetry restrictions faced by the average fishkeeper — and that the whole Dragonfish industry is aimed at people buying and keeping them indoors.
Aquarium size
Using public aquarium expert Jay Hemdal’s swimming space equation (see the article in our July 2009 issue) aquarium sizes for S. formosus are recommended as a minimum of 2 x 1m/6.6 x 3.3’ for a single fish, though an aquarium of 277 x 139cm/9 x 4.5’ would be better.
If you go by our six times tank length and two times tank width recommendations, and Dr Heok Hee Ng’s average adult fish size of 50cm/20” length, we suggest an aquarium size of 3 x 1m/9.8 x 3.3’ for long term keeping.
The aquarium at Bristol Zoo, where the formosus bred, was 6 x 2m/20 x 6. 5’, so although these dimensions may seem ridiculous they are indicative of the levels of long-term care these large tropical fish benefit from.
Housing them in smaller aquaria until they outgrow them and then rehoming them isn’t very responsible.
For the larger Pearl arowana and Spotted arowana from Australia, Hemdal’s calculator based on Fishbase maximum sizes results in even larger aquaria — minimum 2.2 x 1m/7.2 x 3.3’ but preferred over 3 x1.5m/9.8 x 4.9’.
Going by the six times rule and Heok Hee stated size of 90cm/35” maximum length for both species, we recommend a home of 5.4m in length by 1.8m wide (17.8 x 5.9’).
To emphasise yet again, taking the responsibility to keep these amazing fish long term is not a decision to be taken lightly.
Filtration
Considering their size and protein-rich diet, these fish need excellent filtration. For smaller specimens external filters packed with biological media will suffice, though run two in tandem in case one packs up. For mega-sized aquaria, a custom-built filter will be the order of the day. This will comprise a sump and mechanical media, swimming pool pump and either a sand pressure filter for combined mechanical and biological filtration, a trickle tower filled with biological media — or a bubble bead filter will be best.
All biological filters work better when combined with heavy aeration.
If going down the mega tank route, swimming pool-type filters are used often by specialist Koi companies, public aquariums and specialist aquarium installation companies, so do your research before the build.
Such systems can also benefit from computerised monitoring systems and alarms, easy filter backwash and water change facilities, and automated top-up as well. In short, all that kit makes a potentially big job of filter maintenance and water changes very quick and easy, and you don’t even get your hands wet.
Water conditions
Asian arowana live in soft, acidic water in the wild, at a temperature of 30°C/86°F so this should be replicated to provide them with optimum conditions — which may result in better coloration and more readiness to breed.
Pearl arowana like similar hot, acid conditions, whereas Spotted arowana are hardier with regard to water hardness, tolerating conditions up to 8.3 — so neutral to hard, alkaline and cooler water will be fine.
Asian arowana are kept in hard and soft water in the UK, though if I was to spend a sum similar to that of a second-hand car, I would want to provide my fish with the conditions it enjoyed in the wild.
How to feed them
The natural diet of the three Scleropages species varies from fish, frogs, insects, invertebrates and even some plant matter. To get the best from your fish in captivity, feed a varied diet that spans most of these food groups.
In Singapore, aquatic shops sell giant centipedes and live frogs as food for arowana, though we don’t recommend feeding frogs, especially native ones, as the world’s frogs are in danger of being wiped out by disease. They should be preserved where ever possible.
Consider instead a wide range of foods normally sold for reptiles, such as crickets, locusts, giant mealworms, and wax moth larvae. Earthworms would also be suitable.
The Pearl arowana, with its liking for crustaceans, would also do well on river shrimp, and occasional whole prawns. Dried silkworm pupae are available from Koi dealers and may make a nice treat.
Although convenient, large bags of cockles and mussels may not be complete foods for arowana and may also be responsible for the fish putting down fat deposits. Feed a few now and again. Don’t overfeed.
There’s also a wide range of proprietary arowana foods on the market and feeding a dry, complete food regularly is recommended for providing the fish with all the necessary vitamins, nutrients and supplements they may need. Many will also contain colour enhancers that can heighten red coloration.
If your fish won’t accept dry foods, food sticks could be inserted into shellfish, fish or dead insects and then fed, ensuring the fish still receives a balanced diet. Feeding every other day is fine for fish over 30cm/12”in length.
For more information on Asian arowana, check out our picture special which looks at the trade in dragonfish.
This item was first published in the September 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.