Carbohydrates are found primarily in plants and carnivorous fish have problems digesting it. Many herbivorous fish have symbiotic bacteria in their guts which digest the carbohydrates and liberate its energy to the fish. Lipids provide much more energy than do carbohydrates and they also supply fatty acids which are used for the construction of energy reserves in fish. The importance of protein and lipids as energy sources, becomes quite apparent during periods of starvation. In may most cases vitamins are these cofactors.
Vitamins are an important nutritional group which many hobbyists fail to provide for their fish.
Table 1 lists the vitamins known to be used by fish, how they are used and the symptoms associated with a deficiency in that particular vitamin. The marine aquarist should, however, be aware that a failure to provide a balanced, varied diet can lead to vitamin deficiency problems. Similarily, simply providing the deficient vitamin will not result in an immediate recovery, this will only occur over a period of time. The first and most logical solution is to feed them their natural foods. If the tank it setup without fish for a few months, these animals are given the chance to multiply to such an extent that when a few fish are added, the food animals can reproduce at a pace to keep up with the rate of predation.