Yup, mini brittles!
There are a couple of species - well, probably a lot more involved but to keep it simple, a couple of species. But all good to have. Handy little scavengers.
The little white one's with five arms are Amphipholis squamata, and they generally do not get much larger than a quarter or so. They reproduce rapidly...they are a self fertilizing hermaphrodite that broods their young. So one can give rise to many!
The banded one's that you generally don't see except for their legs may be an amphiurid or ophiactid brittlestar. Hard to know for sure, but unlikely to grow particularly large. You won't be overrun with them! And if you are, I'll take some
