What do they look like? Are they small and have different sized legs? Can u get a pic? Most likely Asternia stars which are known for munchin on zoas and such. The best way to get rid of them is with a Hrlequin shrimp. Please research the shrimp first tho, so you can make sure you can care for him after all the asternias are gone.
I didnt relize it was a 10 gal tank lol. Is it just 1 star you see or a bunch? If its small and brown but has longer legs it could be a brittle star, which are good for your tank. Its best to try and get a pic tho, so we can give you a definite answer.
it may be a brittle star. I have one that only came out once as far as I know. Mine generally hides in a rock and only extends its legs out for food. As to where it came from, it is probably a stowaway like mine was.