I have kept perch and pike both in the same aquarium a few years ago in a 6 foot tank, both stunning fish to keep, perch have very nice colours and are extremely aggressive and will swallow anything they can, and the same goes for pike, my largest perch was about 13 to 14 inches and pike grew to over two feet in no time, and i just released them back into the river where i live, i would recomend keeping both these species if you are into predatory fish.