Hitchhiker on snails

[xdcbenoitxd]

I purchased 5 nassarius and 1 sand sifting conch snails a couple of months ago. I put them in my established invertebrate QT to observe. I found something on a shell once and brushed it off as food debris. Unfortunately I was wrong, there are some type of reddish brown worms/algae/parasites on them. Can someone tell me what these little parasites are? I'm sorry for the photos but they're quite small and hard to photograph.

 

[Salt1823]

Looks like a flatworm. If it's flat & reddish brown. Very bad for coral