Getting rid of some Bristleworms will not solve the problem. What is the problem?
Bristleworms are part of the cleanup crew eating dead and dieing stuff. Do you think they were eating dieing Zoanthids? One way to find out is to clean them off with a toothbrush and place them up higher on the rocks in a place of higher flow.
Also, Bristleworms multiply out of control when the tank is being overfed. Do you think you might be overfeeding? How much do you feed?
So, what is the problem?