I currently have two monos that are around 8-9 inches in a 150 along with a silver arowana that is about 12". I recently put the arowana in the tank from a grow out tank where he showed no aggression at all to my small azul, kelberi and broko. Ever since I put him in with the two monos, he has taken over the tank and the two monos hide in the bottom corner of the tank until i come to feed them, then they act normal. Have any of you experienced this in the past? What would you recommend I do to cut down on the aggression? Add some other fish like silver dollars or something similiar? Any input would be appreciated.