I keep hearing about how black arowanas are very peaceful and gentle unless something provokes it. Are they community fish? I'm going to test a 6 inch black arowana with a Jardini about 4 inches, 3 clown loaches each about 2 inches, 2 Jack dempseys both 2 inches and a Ornate Bichir that's about 5 inches. The jardini has never bothered the other fish and sometimes schools with them, all except a oscar that didn't belong to me. Atm they're all in a 55 gallon tank and I plan to upgrade in the future. Should things go bad between the two aros, I'll separate them but has anyone ever achieved this? I'm hoping to start them both while they're still small. Then wait for the dreaded 8 inch mark of my jardini and see what happens then.
Good luck, hope 2 Aro comm works out for you. 