I had that happen last year and there was quite a bit of die off in the shipping box. I cycled the LR
outside of my main tank, using water main tank water in the container and new sw
in the main tank (15-20 gallon changes in a 125).
Day 1 was not too bad but by day 3 it was rather smelly... went through a full cycle.
Personally unless my tank was barren of life and the LR
was first thing in I will always cure LR
outside the tank first. Prevents some unwanted nasties from getting into the main tank too (mantis shrimp, crabs, etc.)