NOTE: THIS IS ONE-FIFTH SIZE. IT ONLY HAS TWO BAGS. Many competing dry salt mixes are not carefully blended. Unless you use the entire bag each mix you produce may not be the same. And when a bag of salt is not used in its entirety humidity gets in and reacts with the salts, producing insoluble residuals that fundamentally change the formulation. AccuraSea1 avoids this problem by having ten precisely measured bags that are small enough you will always mix the entire bag. The Two Little Fishies AccuraSea1 Artificial Saltwater Mix is formulated to simulate natural seawater. It's packaged in two precisely weighed packages. The advantage of this is you can mix up a batch without ever having to check the salinity. No more back and forth adding salt, mixing, waiting, testing and adjusting until you get it right. Simply put a measured volume of water in the mixing bucket, and add the contents of one or more packs (depending on the volume of water).