I hate to be the bearer of bad news, but there's no such thing as a healthy white anemone. If the anemone is white, it means it has expelled all of its symbiotic zooxanthellae -- the colorful algae that live inside its flesh. Plus, a healthy anemone doesn't move. Anemones move to find more favorable conditions, which means either your water quality or lighting (or a combination of both) isn't good enough for the anemone. The only way to keep a bleached anemone alive is to feed it, and there's a chance it can come back if it's fed. But otherwise it's just slowly starving to death in your tank. And when it dies, you risk it killing everything else in your tank with it... That's why anemones are not a good choice for new tanks. They are very difficult to keep alive.