Good old fashioned net. You can even try a clear container or soda bottle along the glass, and chase him into it. Like they do in the store to catch fish with a spec cup. Or... if he's food driven, cut the top off a clear water bottle, turn it inside out so that the neck goes into the bottle, put some food inside and he may end up in there trapped.I had him in my 55 and I think he killed my pistol shrimp that was with my Yasha and scared her out of her burrow. How do I catch him? I am afraid he might kill her