Tank Shut Down Calgary NW

[Nuccio46]

Hi. Just curious i spotted some real strange looking crab in one of my new rocks. Hairy with black head and arms. He wouldn't come out for his perch so I'm thinking he is trouble,plus one other small crab that looks like emerald crab but flat and I think he may be not good as well. I was looking online but can't find what it may be... Then today I found another hermit crab dead... Mmmm soomeone is causing my casualities...any thoughts?
Thank you