I've seen it done in aquariums but as stated they need a lot of space. It is best to start w/ a group of six or more to guarantee that you'll at least have a viable breeding pair. Arowanas' mainly reach sexual maturity at 3 years of age.
Here's a vid of an asian arowana pair spawning in a tank.
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Here's a vid of an asian arowana pair spawning in a tank.
[YT]<object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/5ltmk6oHXg8&hl=en_US&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/5ltmk6oHXg8&hl=en_US&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>[/YT]