HI
Basket stars are relatively easy to keep, given that there are no fishes in the tank that nibble on them and that there is enough food available for them. As they only open when the main lights are out, it is necessary to feed them at this time. While I was living in the US I had a basket star for about 1.5 years, then I sold it together with the entire tank as I had to leave the country. During this time it grew from about 5 to 7 or 8 inches diameter. Feeding was easy, it loved small mysis and other decent sized food. It did not react on any artificial plankton or super fine food like cyclop eeze, it defintely wanted bigger stuff. Now that I live in Germany I would love to get one again , but for some strange reason they are not imported.
Feather stars are a completely different issue. The only ones that have a history of survival in reef tanks are the green ones with rather coarse arms, all the other multi-colored ones or those with real "feathery" arms will quickly fade away. There are a few people that have had some limited success with them, but either out of sheer luck or by making the survival of this animal a full time job. It is still not clear what these guys actually feed on, they do react on certain artificial plancton, but unless somebody comes up with a more definitive method for keeping them, they should be left in the Ocean.
Best wishes
Jens