Do a lot of research before you buy any Starfish.
Some Can't even be taken out of the water EVER! NOT FOR A SECOND! So you have to take special Precautions to NOT expose it to Air.
Also acclimation time is Min 6-8 Hours drip.
You need a whole Acclimation setup for these guys since they will be in there for a while.
I setup a Black 5 Gallon bucket, with a Small 25 watt heater (set to same temp as tank of couse) and an air pump with an air stone set up under the heater for water movement.
So far this has given me the best results. I have 8 star fish.
As a side note, Don't Acclimate more than one star fish together, unless they are the same. I found that out the hard way when I noticed my Sand sifter chomping on my poor little brown tipped.
Anyway Good luck!
If I were you I'd go back to your LFS and demand another one and tell them they should change thier directions for Starfish.