Seachem Stability is used to start up a new tank. This is not neccassary for normal tank cleanings under 75% water change. Anything more than 75% can potentially cause "new tank syndrome" and can potentially kill the fish. This product will be useful in order to PREVENT this from happening. Dosage varies depending on what you are looking to use it for. Read the label for dosing information. Every order of Stability comes with a needleless syrringe for dosing.