brackish

that varies for location to location usually brackish water can be found where the mouth of a river meets the ocean diluting the ocean salt water.

Anything from slightly saltier than fresh water to slightly fresher than full salt. More realistically try to match what the fish came from, for alot of fish the 0.0125-0.020 sg range is good.

Don't Forget - It must be MARINE salt, not Aquarium Salt.

Technically, brackish encompasses the entire realm between freshwater (1.000 specific gravity [SG]) and saltwater (1.021-1.025 SG). Some brackish species, such as bumblebee gobies, silver and New Guinea dats, and archers, prefer the lower end of the spectrum, around 1.005 SG. Other species, such as adult scats, monos, "FW" morays, and green spotted puffers, prefer the higher end of the spectrum, 1.015 or so. As a pratical matter, it may be prudent to keep your brackish water fish near the lower end of the SG spectrum, say 1.005 to 1.010 SG, because most LFS keep their brackishwater fish either in FW or in low salinity, typically 1.005 or less.

Icthy is right, I was at the high end, probably because I used water from where the fish I kept were caught, usually in tidal basins.