When we set our tank up we started with 2 bigger live rocks and the fish store said wait a few days testing the water then get a set of clowns to help with the tank which is what we did and then after a week we got the 2 green chroma and have just been gradually adding stuff. We dont have a mantis shrimp or any big crab. The hermit crabs are about the size a pinky nail with their shells. And as for the rest of the fish everything seemed to be getting along fine until last night/this morning i got up at 240 and checked on the tank since i was already up and everything was fine swimming around