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Fish Nutrition 101

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Fish Nutrition 101
Photo © Michael Rosenfeld
Like you, fish need vitamins to lead long, healthy lives. Unfortunately for too many canned fish foods fail to show the vitamin content of the food. Live foods are an even bigger unknown, as flies and worms are not inclined to prominently display nutritional information about themselves. Even if the nutritional values are shown on the food container label, do you know what your fish needs?

Fat
Fish diets should be low in fat. Even meat eating fish (carnivores) require no more than 8 percent in their diet. Plant eaters (herbivores) need no more than 3%. Excessive fat may damage the liver, and can result in disease and early death. The type of fat also matters, as fish have difficulties digesting hard fats, such as those in beef. Saturated fats are particularly harmful, and should be avoided. Polyunsaturated fats such as those in brine shrimp are the most digestible, and is particularly useful when conditioning fish for breeding.

Fiber
Although small quantities of fiber aid digestion, they should not be too high. Carnivores are not able to digest fiber well at all, and should not have more than 4 percent fiber in their diet. To remain healthy, herbivores should have between 5 and 10 percent fiber in their diet.

Protein
Protein requirements vary based on the type of fish. However, protein is a key element required for good health and growth in all types of fish. Herbivores need 15 to 30 percent protein in their diet, while carnivores need at least 45 percent protein. For vigorous health growth, young fish require a diet that is composed of at least 50% protein.

Carbohydrates
Fish do not need a large amount of carbohydrates in their diet. In fact too many carbs can deter proper growth. However, considerable debate rages over the amount of carbohydrate fish can tolerate without suffering negative side effects. Perhaps the greatest danger in feeding higher percentages of carbs is the resulting reduction in other essential nutrients. This is particularly true in young fish, which need high levels of protein for proper development. Adult fish can tolerate as much as 40 percent carbohydrate in their diet, without ill effects. Most of the carbohydrate in fish food is in the form of starches used to bind the food and prevent it from rapidly disintegrating in the water.

Minerals
Minerals are important for healthy bones, teeth, and even for maintaining healthy scales. The key minerals fish need are calcium and phosphorus. They also need smaller amounts of iron, iodine, magnesium, sodium, potassium, copper, and zinc. Calcium is found in hard water, and phosphorus is found in live plants. If the aquarium water is soft and the tank decorated with only artificial plants, it is important to supplement the diet with foods containing minerals. Bone or meat meal is a good source of both calcium and phosphorus. Minerals have a long shelf life, and can be found in adequate quantities in all good quality flake foods.

Vitamins
Unlike minerals, vitamins are not stable for very long in prepared foods. Flake foods have adequate vitamin content initially, but it deteriorates rather quickly once the container is opened. Storage in the freezer will prolong the vitamin content, however it is best to buy only what you will use within one or two months. Key vitamins needed for good health are A, D3, E, K, B1, B2, B3, B5, B6, B12, C, H, M, and inositol.

Many fish keepers are not aware of the critical role vitamins play in fish health. Lack of Vitamin A can cause back deformities and stunted growth in young developing fish. Anytime a fish is under stress the need for Vitamin A is increased, which can make the difference between falling prey to disease and remaining healthy. Vitamin and E and A are key factors in maintaining fish in top breeding condition. Vitamin K is critical for proper blood clotting.

Vitamins B1, B2, and B6 are important for normal growth. Good digestion requires an adequate amount of Vitamin B3 and C. Vitamin C is also needed for healthy bones and teeth, which are important in all species of fish. Both Vitamin B5 and M are key factors in metabolism. Lack of Vitamin H reduces the formation of blood cells and can cause anemia.

Purchasing foods in small quantities, and varying the diet using good quality dry foods and live foods will help assure that your fish have all the nutrients they need for good health and a long life.

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