Sand sifting stars feed on various critters considered "good" for a deep sand bed. They can, and will, clean a sand bed of many of these animals, perhaps except a coupla inch area near the glass that they might not be able to get to.
They die in a very characteristic manner, by disintegration. They may start just at the arm tips, then large pieces like entire arms may go. At this point, they may be eaten by various other creatures. But until this point, they may look fine and may never move onto the rocks regardless of starvation or not. They take months to slowly starve, by digesting their internal organs, until there really isn't any way to salvage them. It typically occurs 9-12 months after introduction. But seems sudden to the hobbyists.
Many, if not the majority of these stars in tanks under 100g will almost certainly die within that 9-12 month period. People may think they died for other reasons...that it is their normal life span, that something ate them, etc. But it is not normal at all.
Most serious experts on DSB do not recommend sand sifting stars because they eat the microfauna that people are trying to cultivate (to get the whole sand bed to work well).
Some, but not all, may be attracted to meaty foods...or perhaps the things that are eating it. Personalities vary. What does confuse me is that if they are detritus feeders as many argue, why do so few people have long term success with them in smaller tanks? Increased survival definitely seems correlated with increase and tank size and thus increase in surface area of sand which doesn't seem to agree with the detritus argument (there can be a lot in small tanks). :notsure:
