Homey...I've caught one large (silver dollar size) gorilla crab, and several smaller ones (penny size). There are still a few small ones which stick to the higher rocks, and I'll grab those as the opportunity arises. But there is one MAMMOTH gorilla crab who stays on the bottom under the rocks, making him a beast to catch. I WILL get him one day, and believe me he'll wish his mommy had never met his daddy.
I've got at least one, more likely two mantis left. I've captured 5 over the 2 1/2 months since my 1st rock went in. Unfortunately, one of the remaining ones has housed himself in the biggest rock in the tank, in the bottom of the pile. Crafty little devil.