I've got an orange pike(Eater, 6in) in with my midas(Sweetie, 12in). They share a 210 gallon tank with 2 convicts(used to be 5) and a blackbelt. While the smaller fish scrap amongst themselves once in awhile (nothing serious though), everyone moves out of the way when Sweetie swims by, even though Sweetie never bothers any of them.