marine tank

Hi guys, I’m completely new to all this so thought I’d get a second opinion I checked last night all three hermit crabs was out and about doing what they do. this morning whilst doing my checks I found only one crabs carcass or molt what do you guys think?

Its Been 40 days since starting cycling my new tank. I added 4 mollies by slowly converting them to saltwater environment. Its in the tank for the past 5 days they are doing good and taking marine pellets. My question is when shall i add marine fishes and when should i turn on the protein...