[untamed]

Originally Posted by Discustopia

possible Bad news...
check out Ciranolid- a Blood sucking parasite that will attach itself to your fish.
Look at Untamed's post to see if it's close.

Otherwise just a regular Isopod - some tiny - some can reach up to a foot long

Yes, I'm very familiar with ciranolids right now. I wasn't going to suggest that to Colin...but those two black eyes suggest it is a related critter. On the good news side, Colin, Ciranolids are exceptionally fast swimmers. You wouldn't see one just walking around the base of a coral. So the behaviour doesn't suggest that this is a ciranolid.