all water has salt the salt helps produce slime coat, improves gill function, helps inhibit the growth of parasites, softens the water and can help the fish from absorbing things like nitrites i believe? the tap water in my area has a pH level that is reading high every time i test it which calls for the pH balancer (which i only use small amounts to ease off the acidity). also if i dumped the entire 3.4oz bottle into the tank i would overdose her absolutely, which i have not! lol. it is the only one i feel comfortable with using while my tank is cycling as well as when adding new water (i can use more as needed -if needed-). i use 2-3 drops per gallon considering the bottle calls for one cap full for 50 gallons. also the streszyme is used when her tank is cleaned to keep her comfortable if any of the beneficial bacteria has been killed off while adding new water! (like adding probiotics to our diet when we are unbalanced)