so i need to buy 5 inches arowana and 1-2 inches oscar ??Oscars are predatory and grow really fast, so I would tend to stick to arowanas about 2x-3x their length. 4" oscar means 8-12" arowana. An arowana has such a streamlined body as young fish that they can fit in the mouths of other young predators. Someone on here posted that they lost an 8" arowana to a 3-4" redtail cat, or a similar ratio. I've seen 4" oscars eat goldfish not much smaller than 2", and probably about the same body depth as a 6" arowana.
Don't do it.
That would be better, but you should still be careful to be sure the arowana is keeping it's lead on the oscar. Oscars grow so fast that in three months you might have a 6" oscar and an 8" arowana, which could be a problem.so i need to buy 5 inches arowana and 1-2 inches oscar ??