Tonight I brought home my first arowana, it's a 4 inch silver. I placed it in a 75 gallon tank with two 6 inch kois and one 2 inch yellow channel catfish. Everyone seems to be getting along. Aro is eating hikari food sticks and was very happy when I saw him eat tonight. The kois ate their pellets and the aro ate his food sticks, was interesting to see them not fight over the food and eat their own. Will the kois and the catfish be good tank mates? I'll be setting up a 180 gallon tank and moving the aro and was thinking of maybe keeping them all together.