Urban myth 3c is the idea that salt is tonic for fish when it is kept in the tanks at moderate levels (~ 1 tablespoon per 5 gallons). If your fish are the most commonly kept community fish of tetras, corys, angels and such, or even the Rasboras or most Anabantids, these are fish largely from soft acid low-TDS water. It has yet to be explained to me how the average USA tap water, which is at least moderately hard to hard, and alkaline, is going to be improved by increasing those very things in which our water differs most from the natural waters of these fish. Certainly many of these fish adapt well to our local water conditions, and I am one of the strongest supporters and advocates of adapting non-breeder fish to local conditions. This is far better for both fish and keeper than constantly battling sew-sawing water parameters. But the idea that the water is improved for these fish by adding still more TDS goes right by me- I just cannot grasp any meaning to this.