Zonatus are crazy. At 5 inches is where they start getting really crazy. I'd say that 3 Zonatus at 5 inches are gonna kill each other until they get down to 1 pretty quick. But, once you get down to 1 left, I think it'd be OK in a 180 by itself with some dithers.
Let's hope the one that lasts is the best looking one. I have 4 from the same source, and I'm starting to notice that some are more blue than others. I have one that's pretty drab, very little blue, and it's the biggest meanest one of the group.