Sexual maturity is reached between 2-3 years of age. I would give a breeding pair their own 8' diameter pool/pond, with a depth of 3'. They breed between September through November.
There seems to be no sexual dimorphism, although in some arowanas the male will seem to have a bigger lower jaw (because the male is the one who holds the eggs).
If you want to breed arowanas, I suggest trying to breed blacks. At least then you can sell the offspring for much more than the $10-$30 a silver arowana goes for.