Please help me ID this type of Starfish

I have a 75 gallon tank, and I have noticed over the last several weeks that a small type of starfish have started to proliferate. I have not done anything to them, and I have no fish that eat them, but I was wondering what type these guys are, and do they only reproduce by losing a part of their body. They are only around up to around a half inch in diameter, and they have 7 arms.
 
Thanks!
 

 

Neither of these starfish have seven arms right now, but many of the others in the tank have all seven arms. You can tell that their arms are growing back from what they have lost.

They are Asterina.

Thanks

I'll second that. Very common, and a good starfish to have.

-Adam

That is good to know, the tank is being overrun with algae, and I can use all the help that I can get. Are they reef safe, there is a lot of coral in the tank, and they have not eaten any of it.

I believe that they primarily eat coralline algae.

some are reported to eat coral though I never encountered any that did.  I will say I do have some solid reefing friends that did have some though.

I will keep my eye on them, though in the past year they have not eaten any coral, but thanks for letting me know that.

Asterina is one of those families that's gotten a terrible reputation because of one or two bad members. The vast majority of them are reef safe algae grazers that come in on live rock. They do reproduce fast but that's nothing a harlequin shrimp won't handle. You'd likely know by now if they were a coral eating species.

That makes sense, I was researching them online, and it seems like I have a safe species, and it is nice to know that getting a harlequin shrimp will help get rid of them if there are too many of them.
 
Thanks.