Personally, I never ever ever transfer sand from one tank to another. If I were you I would make the transfer leaving the tank bare bottom for a month or so, then add new sand. Or in that time you can wash and "cook" the sand much like you "cook" live rock. The sand bed is sensitive in the way that many of the inhabitants are very delicate and even moving the sand around so the bottom layer mixes with the top is enough to kill a lot of life. Kill life = make cycle. The fish will be ok in the holding tank with powerheads, live rock, and a heater indefinitely as that is essentially a FOWLR, no?
Also, in cases like this I like to use those SeaChem Ammonia Alerts that hang in the tank. You can transfer it from one tank to another, so you can put it in the holding tank, and then the 187 when it is started up too. I have found these alerts to be surprisingly accurate, and are great because they are compatible with Prime in case ammonia does spike.
Does it bother you that your tank is 187 gallons? I mean 187 is the police code for Homicide! It could be a killer tank!! Just sayin...
