i am trying to switch from crushed coral substrate to sand. i have talked this over with many friends and just want more opinions. what is the safest way to do this. i have been warned that my tank will spike. i do have spare tanks if need be that are empty. my tank currently has the following

3 damsels, 1 watchman goby, 1 yellow tang, 1 sea cucumber, 1 cleaner shrimp, 1 peppermint shrimp, 1 sea serpent, many snails, assorted corals.