What is the best method to trap brittle worms ?

[RuGlu6]

Why are you trying to get rid of them?
They are good cleaners for your tank. Especially when food get trapped under rocks and pollute your water these guys are great help.
When i set up new tanks i always get these guys to help keep water clean.
Bristle worms are least of your worries, they don't touch corals or fish unless its dead, but then hey, you want them to eat the dead fish if you don't know about it it will pollute your water.