an animal growing smaller when not in the wild (or when they are in a smaller cage) is a myth.
If proper nutrition and exercise is provided, any animal will grow to full size.
If an animal typically does not grow to full size in captivity, that means that it's needs are not being addressed to 100%.
This applies to angel fish, gold fish, pigs, gorillas, elephants, lions, whatever. It makes no sense that a smaller cage/tank would hinder growth EXCEPT when the animal's development is stunted, in which case the animal shouldn't be caged/boxed in the first place, if you can't provide for its needs.
That said, I think the 180 would be fine for an angel for quite a while until you decided it has outgrown the 180, which would obviously be before reaching Full Size.