Asain green aros growth rate depend on what you're feeding it and how clean your water is. Average growth rate would be 1-1.5" per month then slow down at 14"-16"
I'll separate the aro first till it grows a little bit. That ornate my eat that aro. I used to have a 11" palmas polli and ate a 9" silver arowana. I just notive that the silver aro was gone and the palmas polli is so fat that it can't even touch his pectoral on the substrates. Another case happened to a friend of mine. A 13" ornate ate a 8" jardini. They were together for 2 months and he was shock when the ornate decided to eat the jar during light off.