Niacin (vitamin B3) is a water-soluble vitamin that functions as a component of NAD and NADP — two coenzymes involved in over 400 metabolic reactions in the body. These reactions include energy production from food, DNA repair, cell signaling, and the synthesis of fatty acids and cholesterol. Niacin is, in essence, one of the metabolic workhorses that keeps every cell in a fish's body running.
In fish, niacin is particularly important for maintaining healthy skin, scales, and the mucus coat. Niacin deficiency has been associated with skin lesions and erosion in several fish species studied in aquaculture settings. It also supports proper nervous system function and healthy digestion.
Most freshwater fish can synthesize some niacin from the amino acid tryptophan, but this conversion is not efficient enough to meet their full needs. Dietary niacin from food remains essential. Fish meal, shrimp meal, and insect-based ingredients are excellent niacin sources, and quality commercial fish foods are supplemented to ensure adequate levels.
Quality commercial fish foods provide adequate niacin. A varied diet with different protein sources (fish meal, shrimp, insects) ensures a good supply. As with other B vitamins, freshness matters — rotate your fish food supply every few months.
0.4% of daily nutrient intake
Vitamin B3 (Niacin) makes up 0.4% of your freshwater fish's total daily nutritional requirements by weight. That's a tiny amount — but it matters.
Skin lesions and erosion (particularly on the head and around the mouth), loss of appetite, poor growth, muscle weakness, sensitivity to sunlight (photo-sensitivity), hemorrhaging, edema, and in severe cases, neurological symptoms. The skin and mouth lesions can be mistaken for bacterial infection, leading to unnecessary antibiotic treatment when the root cause is nutritional.
Niacin has a wide safety margin in fish. Excess is excreted in the water and does not accumulate to toxic levels under normal feeding conditions. No practical risk from dietary sources.
| Life Stage | Size | Min | Max | Unit | Notes |
|---|---|---|---|---|---|
| Adult | — | 10 | 40 | mg/kg diet | Fish can convert some tryptophan to niacin but not enough to meet full requirement. Diets with high-quality animal protein reduce the dietary niacin requirement slightly. |
Source: NRC 2011, general aquaculture consensus
