midol, this is just my personal opinion but yes taking wild corals from the ocean is a bad idea. FIrst off your local laws my prohibit this as many coral reefs are protected from collection except in a controlled and managed way. Now you might think to yourself that its just one or two corals and im only one person doing it but that kind of thinking can lead to total disaster of a reef if hundreds of thousands of people thought this way. Our coral reefs need to be conserved and us hobbists are ones whom have alternate methods of getting corals and we should use those methods if at all possible.
Some of these alternate methods include purchasing coral frags
from fellow hobbists. Purchasing corals that have been aquacultured or those that have been rased on 'frag
farms' where the parent coral is several generations out of the wild reef.