small starfish on glass, good bad or just ugly :)?

[Alto]

I noticed this guy on the glass of my tank earlier today and had never seen him before, I have seen them at the fish shop I normally buy from but I havent brought anything new home in over a month. He's on the glass so I am hoping he is okay, maybe just eating algea? If need be I will try and locate him again if he needs to be removed, though I have had the tank set up for 4 months and never seen him before so.... thanks for any help!