I'll unflame you now. Keeping an anemone alive for a long period of time is not impossible, however, requires extreme care, now-how, and a little luck. Some are being propegated in captivity as well. Sponges, on the other hand, are very specialized feeders, and if exposed to air at all, will succumb. You'd probably be best off trying mushrrom anemone's, they are more tolerant, don't require the lighting of LTA,BTA,Riterri, and Carpets. If your set on getting an anemone, probably a BTA for starters AFTER you do a lot of research, and gain experience in keeping various things alive. There's one book that I see commonly recommended, I believe its called "ANemones and Clownfishes" by Joyce Wilkinson (sp?).
Good Luck.