Even fresh water fish need salt. When Koi and Goldfish are healthy, they can maintain their salt concentration in their blood. When fish are stressed, lack of salt in the water can exacerbate the condition. To reduce stress, it's best if the salt concentration of the water is near the salt concentration in the fish's bloodstream.
Ideal Salt Level: 0.1% to 0.25%
Dosage: 1 lb per 100 gal will give a salt concentration of ~0.15%
