Inverts are very sensitive to any changes in the parameters in your water column. The parameters like nitrates, phosphates...so on. If not slowly acclimated to these changes they can get 'shocked' and can lead to death, depending on the vast change, sensitivity of the animal...so on. Some LFS
even keep all of their tanks in hyposalinity, low salinity levels, to help combat ich.
There are a handful of ways to acclimate new arrivals from one system to another, but I think that using some airline tubing to slowly drip acclimate them for 30 min to 2 hours is the best practice. This is something I do to everything coming into my tank, from fish to coral.