From the pictures and videos I've seen of goniopora meadows in the wild, the former is true. In almost all cases, the surrounding daughter colonies are much healthier and larger in size than the previous generation. In certain areas, you can track the number of generations like tiers on a wedding cake and they can take over patches of the reef this way. Here are some more wild photos:Originally Posted by Jessy
Looks like this goni colony has taken over this patch of reef where montis and acros once reside: