how do you know if you have bristle worms?

[Firefliesrscary]

ok so i have a 28 gallon saltwater aqurium with a bunch of live rock, a striped damsel, a dusky jawfish, a chocolate chip starfish and a turbo snail...one of my peices of live rock used to be bigger and like brownish but now its like the rock is disinagrating and underneath the brown rock is this purpley red color...the water levels are perfect. im just wondering whats goin on...

 

[Henry405]

the purpley red color could just be coraline algae. Did you ever see anything stick an arm out?

 

[Firefliesrscary]

its not corraline algea...i know what that looks like...its like the ouside is actually breaking away and its bright red underneath

 

[Henry405]

I THINK thats just how the rock is. Bristle worms are the same size as normal worms, not microscopic