IMO I'd go with a tank of at least 400 gallons and up for this fish. And not fill it to the top with LR. Swimming room is the question here, how much room does a fish need to roam around and have a place to defend + to hide in.
In your case KvcGsxr600, I'd go with the 180 for now OR start saving and planning on a "BIG" tank design to house this fish and other that you will end up getting, cause we all do. Remember a fishes health deos depend on it happiness and well being, if it feels threated do to a shortage of space it will remain slightly stressed out, always defending it's terf so to speak. Once again these are nothing more than IMO's. I'm no expert in the field of fish, just a hobbiest like everyone else.