what are these little guys?

[Nahdurr]

Noticed a bunch of these little guys popped up on the glass and back wall of my nano tank. White spots with tiny several arms coming out.

 

[Uncle99]

Very fuzzy pic.
Maybe Astrena stars.

 

[Dutch_Mill]

Meduda stage of hydroids.

 

[CasperOe]

Looks like Asterina starfish to me, harmless for your tank if that's it

I "breed" then for my harlequin shrimps to eat.

 

[Gtinnel]

A picture that has them less blurry would help, but I would’ve said hydroids too.

 

[kevgib67]

Ya, hydriods, self limiting.