Good or bad work?

[ReefinVic]

Doesnt look like a fire worm but no fish died as of yet. I got like four of these that crawl out to eat sinking foods? Kill or no kill?

While I’m at it, is this a pineapple sponge? The group of white things on the right side of tank.

 

[James M]

Bistle worm and pineapple sponge both good

 

[JasonK84]

The bristle worms are great at eating detritus. Leave them alone and let them multiply. When they reproduce it'll feed your corals and there are some fish like dottybacks and others that will eat them.