This was tank 4, before it was converted into a crayfish home. Yes, it was a salt water tank, and Atlantic nonetheless. The spider crab was actually caught in nearby beautiful Marblehead, while the killis were from a Cape excursion. There were a few shrimp in there as well. All got along pretty well, and then released back to their homes the following Spring. Fellow beachgoers would curiously ask what we caught, and chuckled when we explained it was for the tank, not our stomachs.