Salt is optional for freshwater fish. It is up to you whether to add it or not although in most freshwater fish's cases, salt is not necessary and in the long run, it can harm most fish especially towards those who cannot handle added electrolytes long-term. Those from soft and acidic waters for instance are at a risk of being affected by the salt.Tommydeal;2146272; said:I don't use salt on any of my FW tanks but I'm fairly new to Datnoids, maybe now is a good time to start using salt with my w/c. Is it a good idea to add salt for Datnoids? If so, how much?