The box contains ten gallons of salt, that doesn't mean that the whole box is to be used for a 10 gallon tank, at least I don't think it does. (not sure if thats what you mean, but thats what it sounded like) I added the salt to my tank then the water but when I mix water for changes, I add the salt to the water. You can just pour a little in at a time and allow a PH
to mix. Check your salinity level periodically and add salt as necessary.