Isopod?

[Butcher333]

I have found these twice now. Once on a frag plug and yesterday in a clam shell. They scurry along pretty quickly there are able to swim short distances at least in this bowl used to scrub the clam shell. I’m not able to post a video of their movement here. As soon as I figure that out I’ll update. But one can tap photo zoom for closer look. Any thoughts?

 

[Reefer Drew]

Looks like flatworms. Some are benign and some eat corals

 

[taricha]

Any thoughts?

correct on isopods.

 

[Alexopora]

I have found these twice now. Once on a frag plug and yesterday in a clam shell. They scurry along pretty quickly there are able to swim short distances at least in this bowl used to scrub the clam shell. I’m not able to post a video of their movement here. As soon as I figure that out I’ll update. But one can tap photo zoom for closer look. Any thoughts?

At one glance, I would have said chitons. But you mentioned that they scuttle around and are able swim. I’m going to say, probably a Sphaeromatid Isopod (Sphaeromatidae). Yours look too round to be a Cirolanid Isopod.