Feather starfish are beautiful. Unfortunately their beauty has made them grow increasingly popular in this hobby, but they're lifespan in a home aquarium is very short lived.
These are not starfish that should be kept in captivity, especially for an amateur. Even the most seasoned hobbyists have a hard time with any long term success with this species.
One of my LFS's always orders one and tries to sell them, but they usually die before he gets a chance to sell it, I've reprimanded him for purchasing them time and time again. They're usually not cheap either and are quite big.