Impossible? They're not impossible at all. I know people who have kept them. Assuming you're actually talking about basket stars (not feather stars, crinoids), they just need nightly feeding with a meaty food, such as mysis or krill. In that sense, they aren't any more difficult than fish. The real problem with them, however, is the fact that most of them get HUGE, like 3-4 feet in diameter.