A. Most starfish are not reefsafe and can harm fish and inverts (Chocolate chip,knobby, etc)
B. Most starfish are highly sensitive and get large (For the most part all of them..)
C. Some starfish require a very specific diet and are prone to parasites (Fromia, linkcia)
D. Some starfish, perticularly crinoids are better left for advanced NPS systems. (Feather stars, basket stars, etc)
E. Some get large and eventually starve after awhile. (Sandsifters, etc..)
Despite what you'd expect.. a serpent starfish despite it's much better mobility is safer than the other stars in reef tank around other fish and inverts. Some brittles can be a huge threat (green in perticular). Linkica wouldn't fit.. and fromia needs a very established tank, otherwise those are very harmless.
You would have to target feed all stars other than linkcias and fromias for best and safer results.