I've tried keeping many types of starfish. So far, 1 survives till now (green bristle) since day one. From 2' tank, to 2.5' and then tompang at my brudder's 2' tank and now back in my 4' tank. It was a small star when i first bought it, around 3". Now, 2yrs later... from end to end around 1'. He is my undertaker, keeping the sand clean of uneaten food.
I consider it easy due to its long life and only feeds it market prawn once a week. Don't take my word though. Cause after all they are living things. Have their own character. Can be easy, can be tough.