Commercial fish foods designed especially for koi and goldfish are tested to make sure that they contain the essential ingredients necessary for these species. It's unlikely that the pond owner will encounter vitamin or mineral deficiencies if proper feeding methods and proper storage efforts are followed. Still, it's always better to be informed. Besides the basics, foods sometimes contain additional ingredients such as carotenoids to enhance color. Foods for colder seasons, (spring and autumn), have reduced portein content to aid in digestion during cooler water, lower metabolism, and other more stressful periods. Food with "immune stimulators" or "immune modulators" include ingredients to increase the immune system and the ability to ward off desease. This may be appropriate for short-term use when fish are under stress from show transport or spawning. There is no substitute for proper, long-term care of your fish, including good water quality and adequate nutrition.

Whatever commercial fish food you select, make sure it's fresh. The vitamins and minerals in fish food naturally degrade somewhat by the time they reach you, the pond owner. Vitamin C is a prime example. It's one of the most important vitamins for fish nutrition, but it degrades as the fish food ages. Over the last 10 years, stabilizers have been created to make the vitamin C longer-lasting. Just the same, it's best to buy food that hasn't been sitting on the shelves for a long time.

Commercial pellets are the best type of fish food for the steady diet of koi and goldfish. Young fish should be fed flaked food until they are large enough to eat regular pellets. Commercial foods have the best mixture of ingredients to ensure that your fish stay happy and healthy. You can make your own food at home, although it can be expensive and rather labor intensive. Koi and goldfish often enjoy supplemental food such as peas and oranges. These are "snacks," though, and shouldn't become substitutes for all-around, good-quality commercial fish food.

The quality of the food you select will last longer if you take good care of it. Proper storage and handling is vital. Exposure to warm temperatures, sunlight, or metal will cause the food to degrade more quickly. Several vitamins will be depleted, some of them rapidly, when the food is stored at a warm temperature, or in sunlight, or in a metal container. Moisture is another problem. Exposing the food to moist conditins can cause molds, and some of them can actually be toxic. It's best to keep fish food in dry, cool, dark storage conditions. If you have a lot of food, put the surplus in sealable plastic bags and keep them in the refrigerator or freezer until you need it.

Mishandling fish food can even lead to health problems. Fish foods always contain a certain amount of fat. If the food is kept at room temperature or warmer, the fat can oxidize and the food can turn rancid. This can cause several illnesses, including liver damage. You won't know that the food has gone bad. It won't change in color, appearance, weight, shape, or smell. Your fish will know if the food is rancid, but you won't be able to tell a thing until it's too late (except in extreme cases). Whatever you do, don't leave the fish food in an open container at the side of the pond so that it's within easy reach to feed your koi or goldfish every day. It may make feeding easier for you, but it will make eating well, much more difficult for your fish.

As for floating and sinking food, floating types are good for koi and most common goldfish. Floating food allows us to watch the fish while they eat. Koi usually like to feed on the bottom of the pond. When they come up for floating food, we can see them more closely. We have the opportunity to inspect them for ulcers or other problems, things we don't notice so easily when the fish are swimming deeper in the pond. Sinking food doesn't give us the chance to see the fish as easily, or to make sure that they're eating everything we feed them. It's also much more difficult to remove uneaten pellets from the bottom of the pond.

Sinking fish food, or semi-sinking food, (it drops more slowly to the bottom), is better for many kinds of fancy goldfish, (not comets or sarrasas). Fancy goldfish can more readily encounter problems when they eat a dry, floating pellet. Their body shapes have become distorted after years of selective breeding, and this affects their internal organs. A fancy goldfish that eats a dry, floating pellet can have a reaction similar to the robin that eats a piece of uncooked rice left over from a church wedding. Once the goldfish eats the floating pellet, the food absorbs water and expands in the fish's digestive tract. As the food gets larger, it can get impacted and causes all kinds of problems, including swim bladder malfuntion, constipation, and even death. If you have fancy goldfish in your pond, soak dry, floating pellets in a saucer of pond water for three or four minutes and then pour the food into the pond.

One common way to calculate the amount to feed an animal, including commercially reared fish, is based on their body weight. This is often done for pets such as dogs and cats. Manufacturers recommend so many cups for every so many pounds that the dog or cat weighs. For koi and goldfish, it's not so easy to use their body weight to decide how much to feed them. It's cumbersome, difficult, and sometimes very inaccurate. Who wants to do the math to calculate the weight of each fish and multiply by the number of fish who have that body weight? Besides, koi and goldfish are cold-blooded. They eat very differently depending upon water temperature, air temperature, even barometric pressure. Natural variations from day to day and as well as the larger, seasonal cycles of nature all affect how much your pond fish eat on a particular day.

It's much better to watch your fish and their eating habits and feed them as much as they can eat in about 10 minutes. If they're eating well, they'll show it. Their color will be bright and they will have a nice sheen to their skin. They'll be active and well developed. This is really the more sensitive and more sensible way to take care of you koi and goldfish. Feed them by hand, not by an automatic feeder. That way you can look them over as they come up to eat, and avoid overfeeding.

How often should you feed your koi or goldfish? Your fish do better if they eat in smaller amounts several times a day. Smaller meals allow the digestive track to take care of all the food efficiently. Of course, there's a limit to how far you should take this. Most pondkeepers are unwilling to quit their jobs so they can stay home and feed their fish all day long. (How selfish are these pond owners, anyway)? Try to feed your fish at least twice a day in the summer, more often if you can, and always at about the same time, day or night.

Remember, having eyes that are bigger than the stomach can apply to fish, too. Their appetites can sometimes take over their ability to absorb everything in the food, especially in the spring. It's better to underfeed them a little, but not by much. There's significant evidence that koi and goldfish live longer if they are only fed about ninety percent of what they would normally consume on a regualr basis.

Underfeeding your fish just slightly has additional benefits. Koi and goldfish profit from between-meal browsing on insects and algae in the pond. They get important nutrients from these natural snacks in the water. If your fish are not filled to satiation from the food you give them, they will be encouraged to seek these other, natural sources of food in the pond water.

Another aspect of quantity is the size of the pellet. Don't use a pellet that's larger than the mouth of your fish. It's not good to feed large food to small fish. The smaller fish tend to play basketball with the large pellets, pushing them around the water surface. This might be fun for us to watch, but it can actually cause mouth lesions on the smaller fish. Besides the risk of medical problems, they often aren't really getting any significant amount of food. Larger pellets are good for larger fish. it's easier for them to find the larger pellets so they don't float away, dissolve, and foul the water. If your fish range in size, use food of different sizes or settle on a small size pellet which you provide in sufficient quantity to satisfy all the fish, including the largest.

Overfeeding your fish also taxes the filtration system in your pond. The uneaten fish food quickly fouls the water and causes problems of ammonia or nitrite buildup. When koi or goldfish eat more than they should, they aren't able to digest everything. Much of the food becomes fecal matter that affects water quality and pond filtration. Moral: Don't overfeed your fish, and net out any food that's left uneaten.

Low-value fish food can cause problems for your fish and your pond, too. These foods tend to have more filler and less important, nutritious ingredients. Your fish may eat more of the low-value food because it has less nutrient value per pound. Of course this will lead to more fish waste in the water, placing a strain on your filter. It also creates an environment more suitable for parasites and other pathogens to prey upon you fish.

Algae is another by-product of poor fish-feeding habits. As the fish waste and decomposing fish food foul the water, algae is given a chance to take hold in the pond. Phosphorous promotes algae, too. This mineral is important to fish growth and is included in most fish foods. Koi and goldfish don't always digest or absorb it well, and whatever is not used is returned to the pond water. Unfortunately, algae need phosphate to grow as well, and take up the excess that the fish have placed back into the water. Many fish food manufacturers are now incorporating enzymes into their food to help the fish digest the phosphorous more completely. This, in turn, has allowed the manufacturers to reduce the overall amount of phosphorous that they include in their foods The fish are able to absorb what they need, and less is put back into the pond.