what are the diffrences in the 2 worms? what do i look for ? these worms are kinda red and have little bristally things on them.. what type of worm would the be? the live in my live rock and only come out at night when the lights are out..what is a halichoeres chrysus? and what is a coris? never heard of either of these ...
While the bristle worm can leave it's bristle in you - duck tape helps remove it. The fireworm - typically of a red coloration has poison in its bristle and while not threatening (except for allergies) can leave a troublesome rash to deal with. Fireworms (no experience, but have read) that they are more predatory and the bristle (more common and lots of experience) are beneficial unless the get to be a population control issue. I don't have any small ones in my display tank - but have a 6" that has been there for a while. Good for keeping down the detritus and cleaning the holes/pores inthe rocks. Won't harm anything alive.
Bristle worms do provide environmental info on your system. If you overfeed then the population will grow to work with the excess - if they don't have excess food they starve and depopulate themselves.
As for the Halichoeres chrysus (Yellow Coris)
https://www.bluezooaquatics.com/productDetail.asp?did=1&pid=1031&cid=289 it is a natural predator and beautiful fish - burys in the sand at night - bright lemon yellow about 4". Six-line will also work on bristle/flat worms. I am big on natural predation not the use of chemicals. If you look at wrasses you will find many are a good predator for these worms. Make sure you are looking at reef safe if your system is a reef.
If you google "Wetwebmedia" you can get a lot of information on these worms and others opinions on their risks/benefits. Hope that helps!