I would smell your water... If it smells like rotting fish I would take the anemone out.. is he sticky at all ? If not he is probably on his way out the door. What type of lighting do you have it under?
What is your tank parameters ? How old is the tank? Has the anemone ever actually planted its self? What is your flow like?
If the anemone die's in the tank it is not going to be good.. If that happens I would do a large water change, new carbon, up your skimming, wait a day while your water mixes and do another change. This is just my two cents and my experience with my first try at an RBT.