Here's a qoute from another thread. I had it backwards... use a higher salinity mix:
Originally Posted by
Saltwater8
Before (or after) curing your newly arrived live rock, you can submerse the new rock into a bucket filled with saltwater with a specific gravity of 1.035 to 1.040 for one minute. Any invertebrates including: mantis shrimp, bristle worms, and crabs, will quickly evacuate from the rock into the bucket of water. Bristle worms still attached to the rock can be removed with a pair of needle-nosed pliers or tweezers. After removing the live rock from the bucket, you can then sort through the invertebrates in the bucket that you will want to add to your system, and discard all of the unwanted pests.
And yeah if you find him let me know. I got an empty tank sitting here and have always wanted a mantis.