This worked! Rather than measuring, I just put the rock in a 2g bucket with tank water, and added a quarter cup of salt, stirred, and waited. Rinse and repeat. Got up to 1 full cup before he scooted. The refractometer was up to 1.060. Here's the little troublemaker, going into the soon-to-be refugium.Simpler alternative. Take rock, place in heated saltwater at a gravity of 1.040. Dunk it for a minute or two. If it's still happy after that time and hasn't ejected. It deserves a medal.