I swithced from "cheap" brand, can't remember what it was, to Instant Ocean. It is completely dissolved within a day (however, I still prepare it 4 or 5 days before use. I don't believe they are all the same. They all have salt, but there's lots of other critical trace elements in the mix that may or may not be there on some brands. For the sake of stability in the tank, I'd send it back and go back to what works.