Vitamin C

It is well known that Vitamin C (Ascorbic Acid) helps the body fight infection. In fact it has been proven that levels of 2,000 mg of Vitamin C for every 1 kg of food will render fish much more immune to a wide variety of infections. It also helps them pull through transportation and other stressful situations without falling ill. This is because Vitamin C speeds up wound healing, and causes immune cells to respond quickly to an infection. It also helps in the absorption of iron from the intestines and strengthens blood vessels.

Since Vitamin C is highly unstable, koi feed cannot be stored for too long in warm humid conditions or in the sun, otherwise deficiency will result. In recent times some manufacturers have been using a stable form of Vitamin C (Ascorbic Acid Polyphosphate) which is equally effective, and remains stable within the feed for much longer.

Vitamin E

Vitamin E is an antioxidant. Simply put, it helps to stabilize the membranes surrounding each cell, and to protect cells from being damaged by toxic by-products. These by-products are formed during digestion, upon exposure to toxins in environment, or when fish are fighting off infection. Vitamin E is an essential component of a complex protective mechanism in the tissues. In particular it protects red blood cells from disintegrating. This all means that with adequate doses of Vitamin E, the koi is more able to tolerate stressful conditions and resist infection. Gills will not bleed as easily, and skin colour may improve.

However its level needs to be balanced carefully with a mineral called Selenium for optimum results. This is often overlooked in koi diets. Too much Vitamin E can also be toxic. Furthermore the type of Vitamin E is important. Natural Vitamin E is more readily absorbed than synthetic Vitamin. Try to look for feeds which are rich in natural Vitamin E, such as those containing corn or wheat germ.

There has been a lot of talk about polyunsaturated oils (HUFA’s) such as oils from fish or crop seeds. People need to know that in our warm weather, the higher the oil levels, the faster koi food will become rancid. Even very slight amounts of rancid oil present in the food, undetected by smell, will cause serious harm to koi. Vitamin E prevents the feed from becoming rancid during storage and helps protect the fish tissues from harmful effects should any rancid feed be inadvertently eaten. Manufacturers often add Vitamin E into the feed for this purpose. However try to select those with added natural Vitamin E (d-alpha-tocopherol) rather than the synthetic form (dl-alpha tocopherol) for more effective results.