From the time they hatch, to when they are about 14-15 inches (assuming your talking about silvers) is when these guys grow the most, and that is the reason why they need more nutrition. Therefore, i suggest 2-3 feedings a day is enough. Just feed them until they will no longer take the food. Once they get past this size, you can begin to reduce the feeding interval. Full grown arowanas should be fed only 1-2 times a day.