Arowanas are rumoured to breed in mud ponds only. That is however a rumour. The main reason that they don't breed in fish tanks is because of the food. They need plenty of live food to get into the mood, a mud pond allows that because insects like centipedes,crickets,grasshoppers and many other creey crawlies fall into it all the time like a constant food supply. Less arowanas breed in concrete ponds than mud ponds for the same reason. Concrete ponds have a walking edge at the sides of the ponds so less insects fall in. Mud ponds have grass and vegetation up to the very edges of the ponds so more insects fall in.
By the way this is though research I did and is just a thought. I DO think this is a POSSIBLITY though.
By the way this is though research I did and is just a thought. I DO think this is a POSSIBLITY though.