as long as u still see yellow, it is fine, once u see the yellow fading to white, then its kinda over for its life.
I do not believe this is true. About 5 months ago, I was given a pure white purple tipped sebae anemone as well as a clark's clown. Knowing that this anemone was bleached I could only be hopeful for its future. The anemone also was not "sticky" to the touch and didn't react when I touched it (which worried me). However, it looked stunningly beautiful and the clownfish absolutely loved it. I acclimated it and threw it in my tank. It wasn't long before the anemone wedged itself behind a rock, receiving absolutely no direct lighting at all. Within a short time, the condition of the anemone seemed to worsen: it took on an almost transparent coloration, not white but clear.
Knowing that the anemone was not being nourished by any zooxanthellae, I had been trying to feed it heavily. Every day I was offering it krill, silversides, squid, etc with no luck at all. The anemone seemed to have no interest in any food. The clownfish was also diligent in trying to feed it but it seemed that the food was simply blown off of the "non sticky" tentacles. I was expecting the worse.
However a few weeks ago the anemone once again relocated. This time it came right out in the center front of the tank (receiving direct lighting). I inspected the anemone and was happy to see little brown dots starting the cover the tentacles of the anemone. I was glad to learn that the zooxanthellae algae was returning. I quickly grabbed a piece of krill and placed it within the anemone's tentacles. It quickly and voraciously pulled it to its mouth. I was very excited! Since then, the anemone is becoming more and more brown spots and covering the anemone. I am fortunate and very excited that it has recovered.
However, as Fluff mentioned, apparently it is not totally impossible for an anemone to survive without its zooxanthellae. I read an article posted on another webpage which explained how someone had been keeping anemones for years with little to no light at all. Fortunately anemones are able to receive nutrition in more than one way: zooanthellae algae, plankton, unexpecting fish or invertebrate, nitrogeneous waste of the clownfish. The author of the article insisted that if the anemone is fed heavily enough, it does not need any zooxanthellae to survive. He explained that the anemone could be as white as snow and still be receiving all of the nutrition it needs. Just something to think about. HTH