Arowana, because of its strong territorial consciousness, may have two in a fish tank, and there will be fighting. This fact does exist. So many people will keep one or three arowana in a tank.
This is indeed a singular number, so it has been hyped by some people with ulterior motives. Arowana can't keep even numbers. What will happen after raising it? Bullshit! Say the fish tank can't be higher than the heart. Do those aquarium owners who are higher than their hearts worship them?
If you keep two arowanas, you will fight. Can't I keep four, six, eight and ten? Is it illegal? If you are an ornamental fish lover, please don't ask whether raising fish is odd or even, and give those so-called charlatans a chance.