Cerianthus tube anemones are not photosynthetic. In fact they are not really anemones either but cousins of the true anemones.
Cerianthus Tube Anemone.
The tube anemone on the picture is one of the few creatures that has survived the power blackouts. Probably the fact that it does not require light to live has helped a lot — the only other cnidarian that has done similarly well was the Dendrophyllia coral, which also does not require light.
A Cerianthus tube anemone still living and looking healthy even though nearly everything has died around it in the tank during the power blackout.
Cerianthus tube anemones prefer to be active at night, they scavenge food scraps and prey on animals that they can overpower, although they mostly eat rather small prey. Contrary to the popular belief they will not eat all your fish.
Tube anemones don’t have a pedal disk and cannot attach themselves to rocks. Instead they live in tubes made out of their own secretions, nematocysts, and sand particles. Tube anemones require a deep enough enough sand bed to bury their tube in it.
Further Reading:
Aquarium Invertebrates: Tube Anemones