Foods and Feeding
Koi are cold blooded animals and so their metabolism is very dependent on water temperature. Ideal water temperature for koi is 62 degrees through 84 degrees. At 70, food will pass through a koi’s system in about 2 hours, at 60 it takes about a day. Below 45 degrees, digestion stops and over 90 degrees food passes through so fast that the koi get no benefit from it and it only fouls your water.
As water temperatures go up in the spring you can feed your koi more often. Our recommendation on feeding is to start feeding once a week when the water temperature is between 45 and 55 degrees, twice a week for temperatures between 55 and 60 degrees, three times a week for water temperatures of 60 to 65. From 65 to 70 degree temperatures we recommend daily feeding, up to twice daily for 70 to 75 degree temperatures and up to four times daily for temperatures of 75 to 85 degrees. At 85 to 90 degree temperatures, drop back to no more than one feeding daily and when the water temperature goes above 90, stop feeding altogether. Floating thermometers are available for ponds, as are wireless digital ones that can give you a pond temperature readout inside your house.
When going on vacation, if you are going to be gone for less than a month, the best thing to do about feeding your fish is nothing. The worst thing to do is get someone unfamiliar with your pond to feed your fish. Overfeeding will cloud your water, overload your filter and potentially harm your fish. Your fish will find algae, plants and insects and insect larvae to eat while you are gone, and can easily go for weeks without eating fish food. Vacation feeding blocks are available, but even the manufacturers of these admit they are just to make the fish owner feel good. Auto feeders are available for people who will be gone more frequently or otherwise cannot feed their fish on a regular schedule.
Because you should not feed when temperatures go below 45 degrees, for this area we recommend stopping feeding at Thanksgiving and restarting around St. Patrick’s Day. Temperatures may be high enough to feed a week or so either side of these dates, but it will do no harm to start and stop on these dates anyway, and they are easy to remember. To prepare the fish for not eating all winter, you should feed a high carbohydrate or wheat germ food for at least six weeks in the fall to build up their fat reserves. You will want to feed them this again for about two weeks in the spring to replenish their fat layer before switching to a high protein summer diet to build muscle mass and help the koi grow. When switching foods, the transition is helped by mixing the two foods together for about a week or so. Keep in mind that your fish need at least two weeks for their metabolism to speed back up to the point where they can safely eat. Two or three days of warm weather in the winter does NOT mean that you can feed your fish, even if they beg for food and “well, the book says I can feed them if the temperature is over 55”. Remember, your kids want to eat the whole bag of candy at Halloween, but if you let them, they will get sick.
There are two basic food additives to brighten fish colors. Most color enhancing foods contain a combination of spirulina algae and ground up shrimp, lobster or other crustacean shells, which tremendously brighten the yellows and oranges on your koi. Koi clay as a food additive contains micronutrients that deepen and brighten darker colors like the reds, browns, blues and blacks. Koi clay also helps the digestibility of food. Some of the better foods add microbes to help the digestibility of their food. The better the digestibility, the less waste for your filter to have to clean up.
In general, the higher the protein content of a food, the better it helps build muscle and helps with growth. The higher the corn or filler content, the more it just turns a fish fat.
Foods typically are available as pellets, sticks or flakes and floating or sinking. Our recommendation is for pellet or stick foods, as flake foods for koi or pond goldfish are harder to eat in the volume they should have. Koi and goldfish are both natural bottom feeders and so a sinking food is a more natural diet, but a floating food does them no harm, is just as healthy for them and much more fun for you as the owner to watch them eat.