Bloodworms are actually what I meant to say.

I'm not really an expert here but I suspect the coloration has more to do with temperature and stress levels and it could indicate illness but I don't know what to look for other than the obvious.

I've been using gravel vacuums since the late 80s, literally thousands of times and that was the first time I've ever hurt anything. These little guys just aren't that fast, don't see well, and don't always get out ta the way.