I believe the theory is that 1.008 - 1.010 is closer to fresh water, than it is to marine water. Either way, the bacteria contained in the package are not acclimated to the conditions of my tank, so I suspect the Bio-Spira may take longer than advertised. I anticipate that some of the bacteria population will die from the change in salinity. If I had it to do over again, I would start with fresh water, add the Bio-Spira, then slowly increase the salinity over a couple of weeks. This would give the bacteria population time to acclimate, and give the hardy bacteria time to reproduce.