I have a lot of trouble distinguishing bristleworms and fireworms (which are a type of bristleworm). I do have a few like the example above, just about 10 cm long when stretched out, and some days I think they are one kind....next day, they look totally different. I have spent hours and hours trying to identify at least the family.
These guys will savage a (dead) cockell - just rip it apart. But I've dropped hermits, small snails and the like near their "cave" (actually, they live in the case of a powerhead....) and tho' the worms seem quite excited and swarm about, they never eat the live stuff. To be honest, I don't think that their senses nor their speed make them very good predators - I think they'd love to succeed but just can't raise their game.
A couple of these can easily eat a cockle between them....makes them wonderful scavengers IMO.
Ron Shimek says that fireworms are, like bristles, also good reef tank creatures, with the exception of one found in the Atlantic, Hermodice carunculata, which will eat corals.
Having said that, if I found a 30 cm worm in my tank I'd definitely be testing his hunting instincts and aptitude ! How did he get so big....
Once I get a digicam I'll post a pikkie and find out what I am feeding !
kim