it generaly takes much longer than a half hour for one to die dude, keep in mind they will look real crappy. even if happy when first introduced. u prolly threw away a live anemone. even if dying they show signs of death extremely slow, not in a period of hours but days. and generaly once u start seeing signs its too late. make sure the water is chlorine free and give it another shot, they will look terrible, almost inside out once or twice a day, they arent dying they are juss taking a dump. be careful and keep an eye on them at first wait over night, it takes a while for the toxins they secrete to actually come out of thier bodies anyways, it comes out as they decompose, so introduce, keep an eye on them and give them over night, you will see a difference come the morning.