i have had zoas that grow together and make a stalemate with each other, and then one day you will notice that the __ zoa is way over in the middle of the other zoas and I wonder how it got so far over the other side...no harm in fragging if you are worried that one is taking over the other though
^+1 i have some zoas that are brown with white centers and i have green ones with purple centers and they are right next to each other and the green and purple ones are now in the center of the brown and white ones.