found a starfish where could it come from

[jkenosh]

i was looking at my 29 biocube which has been runnin for about 1 year and i looked over and saw a small starfish on the glass, where could it of had come from, i havent added anything and have never had this type of starfish, i do have 2 brittle stars but this looks like a baby chocolate chip

 

[5380]

Is it an asterina?