yeah id have to agree^... 4 silver arowana are gonna need a lot of space to freely swim around without feeling overcrowded. They're extremely active fish, but the problem is, as everyone knows, theyre topwater and stick to that area, occasionally hitting the midwater. So 4+ arowanas, no matter the depth, are going to feel very claustrophobic, which may lead to aggression issues. Id stick to 3 honestly, thats what im doing. But to everyone their own, with enough space it will work im sure.