Also, if you acclimate them yourself, then they are a true canary in the coal mine and will let you know if you have any diseases or parasites in your system, as they won't have any immunity to saltwater pathogens, etc. But, if you get them fully acclimated, they will have likely built up immunity already. You can acclimate them in hours or over the course of a day, which is better. Just put them in a 5g bucket with an airstone and drip away. Start with just an inch or two of fw, then remove half of the water when it's doubled. Do this until they reach your tank's salinity. I've done this since the early 80's.