I've done it both ways. Both seem to have the same affect, Browning and blackening, under one condition, when the polyps are dipped open.
I have found that the trick to this stuff is you must force all the polyps to close. ALL OF THEM. The muscle that constricts the polyps closed, will protect zoanthid/paly from having all its chloroplasts killed.
Otherwise, you will kill whatever you dip open.