Weird bugs on my sps

[akm]

I've noticed these weird black "bugs" popping up over a lot of my acros and montis. I pretty much only ever see them on or half inside a closed polyp, which seems like a pretty bad thing. I can't tell if they are flatworms or what, anyone ever seen these?

They are kind of hard to see in the picture but they are there.

[aquadoc]

Maybe a Acro eating flatworm. Do you notice loss of growth/color?

[akm]

I haven't noticed a change in anything, also aren't acro eating flatworms white, or is that just the monti eating ones?