Shaping zoa

I see tons of pictures of zoa colonies that are rounded. How is this done? Mine are currently on a frag plug. Do you get round rock? Forgive my ignorance

Mine grow in a straight line and then fill in making the rounded look like a phalanx if that makes sense.

If you have one polyp and it grows 4 more and then those grow 3 or 4 more pretty soon you get that rounded look.

Take a pen and try it and see what shape you get.

Also there was an article in Reef Hobbyist maybe two editions ago that discussed why corals grow they way they do.

The colonies look bigger than a frag plug

Large colonies are on rocks, they are exagerating the shape of the rock be growing outward to out compete the neighbors. Limited space for the polyps so the grow longer, thus giving the round appearence..