Are these both bristle worms?
 

there is a larger one that comes out whenever is feeding (about the girth of a small finger and 5" long or maybe more) These ones are much smaller and lighter in colour. is it fine just leaving them as part of my CUC? thanks.

No Problem!
 

There bristle worms for sure, some people think because they are not eye pleasing they should be removed from the tank. It's part of what's in the ocean and they help clean up trapped food and detris. I have them and they have never been a problem in my reef tank. I say leave them alone. :biggrin:

^^^ I also agree. Leave them in the tank. It is part of the whole circle of what is happening in the tank :)

They do no harm to your tank per se and you can leave them in there but I personally don't like them and do my best to keep them outa my tank.

watch out for the wicked bristles - if you do catch them, go for the middle of the body with tongs ; or if you try moving a frag, there might be small ones hiding underneath. They do multiply so getting rid of some is a plus.

I keep the smaller ones. The 5 in one I would get rid of.
They are a great CUC and do a good job. If you have lots, then maybe you overfeed. The population will reflect how much they have to eat.
But I would not trust a 5 in long one ...yeeks

thanks for the responses:)
 

is there a 'trick' to catching them with tongs? They seem very good at hiding themselves in LR, etc.

Also, are they fast and aggressive when being sought by tongs?

make a mini "bag" out of an old nylon stocking. Put a bit of food in it, ie a piece of shrimp. The bristle worms will snag their legs on the nylon and be caught.