Dont you mix it up the day before? YOur supposed to mix it approx 24 hours before a water change. After you let it aerate with a powerhead for a while then check the salinity to make sure that it is the same as your tanks salinity. You are also supposed to have it in a vat with a heater so that the temp is the same. I hate to be negative, but I doubt this would be very good for your fish, let alone your fish. Assuming that your salinity was 1.025 I wouldnt bet that your organisms would survive.