From a website, gotta feed it:
The Tube Anemone is best kept in a reef with a soft, deep substrate. It creates its tube from the nematocysts that it has discharged. Their coloration is highly variable and the most popular colors are bright orange, bright purple and bright green. The ideal aquarium for the Tube Anemone is one with a deep sand bed, plenty of live rock and a refugium for a natural food source. They are non-photosynthetic and do not require intense lighting. In fact, they are nocturnal in nature and will take time to begin to open during the illuminated hours. Because they are not photosynthetic, they need to be fed regularly when it is fully expanded. Feed small frozen foods such as brine or mysis shrimp, chopped pieces of fish and zooplankton.