When to feed koi and goldfish

Feeding time is probably the most enjoyable and rewarding pondkeeping activity. However, when you feed your fish is as vital as what you feed them.

Are there variations in feeding times depending on the time of year?

Koi, like all fish are cold blooded and their metabolism (body tick-over) is determined by water temperature. Koi are more active in Spring/Summer, feeding and growing well but falling into a state of ‘hibernation’ in Autumn/Winter when they stop feeding completely.

During the months of February and March, fish are reviving from their winter rest. Feeding time is the first time in months that you will have seen your fish and it is an ideal time to inspect their health. Remember, they have not eaten for several months and are at their most susceptible.

Is there a time when you should stop feeding completely and when should you start again?

Water temperature determines both the quality and quantity of food offered. Koi should not be fed when temperatures fall below 8oC as research has shown that koi cannot digest their food at these temperatures. Resist feeding during isolated warm sunny spells in autumn and spring. A lower protein diet should be offered as temperatures fall to 8oC heading into winter and when they rise above 8oC in spring. Lower protein diets are generally easier to digest and a higher protein content is not required at these times as fish are not actively growing at these temperatures. In the warmer months from April to September a higher protein diet should be fed to encourage growth and to allow fish to lay down reserves for the winter. Fish should be fed what they will eat in 5 minutes. This of course will be more in the summer than the winter.

What happens if you feed when you shouldn’t?

It is often tempting to over feed eager feeding fish. Koi are descendants of the carp, which are browsers by nature, constantly sampling, tasting and rooting around the pond bottom. They prefer to be fed a ‘little and often’, coping and digesting the food more efficiently when fed in this way.

If the food is offered when too cold then the food will remain uneaten in the pond, begin to breakdown and pollute the water, leading to water quality problems, ultimately stressing the fish. If koi are fed during an isolated warm spell that is followed by a cold snap then there is a possibility that the food remains in the gut and begins to rot, potentially leading to intestinal and digestive problems.

What are the benefits of feeding on time?

Koi are reasonably intelligent and can even be trained into feeding themselves by operating a demand feeder. Similarly, koi can associate certain times of the day, noises (back door closing) or even footsteps with feeding time, causing them to respond by swimming to greet you. It is at feeding time that koi and other pondfish can be inspected to assess their behaviour. A change in behaviour can often be the first indication of a health problem or may be in response to a water quality problem or even the attentions of a heron or a cat. Try to feed at the same time and in the same place to build a ‘relationship’ with your fish, making it easier to spot and pre-empt any potential problems.

Are there things that are beneficial to feed koi and what are they?

Koi should be fed on a well balanced diet, of the correct pellet size that can be easily swallowed. The benefit of feeding a commercial koi diet is that all of the dietary requirements (proteins, oils, carbohydrates, vitamins and minerals) are provided. It is prudent to choose diets that have a recognised vitamin C content as this vital vitamin is easily lost in the manufacturing process.

Try to avoid giving koi whole food treats such as sweet corn, bread and lettuce as the enjoyment with which some of these ‘human’ foods are consumed is not necessarily reflected in their digestibility or their benefit to the fish. Koi can also become quite fussy, as they will often not appreciate a change in brand having eaten another for some time.

Are there things that bring out the colour more than others?

Another significant role of the diet is to enhance and improve the skin colour. Some diets boast colour enhancing properties while others do not. Colour enhancing additives included in the diet may include spirulina, krill, chrysanthemum meal and some synthetic colour enhancers such as astaxanthin. Colour enhancers cannot bring out colour that a koi does not already show but can only enhance existing colour. Q. I have seen many different pond foods with protein contents ranging from 20% up to 45%. Is there an ideal protein content I should be looking for?

A. Lower protein diets are fed at lower temperatures (8-12oC) in autumn and spring when digestion is less efficient and when the fish are growing less. Wheatgerm diets are popular, offering a low protein level in an easily digestible form of protein.

Higher protein diets are ideal for summer temperatures for good growth and storage of food. Be careful when feeding high protein diets as these richer diets can easily lead to water quality problems.

Q. A friend of mine regularly feeds his pondfish ‘treats’ such as peas, bread and even prawns. Is this standard pond keeping practice?

A. Proprietary brands of pond fish foods offer a balanced and well-researched diet. There are no nutritional reasons why ‘treat’ foods should be offered as they are not providing your fish with nutrients which they are deficient in. There may be a merit in terms of offering a variety of diets but be careful as certain whole foods may cause excessive fish waste and in some instances may cloud the water (e.g. bread). If you feel inclined to try a treat food then offer it in the summer and make sure they do eat it and it doesn’t sink to the bottom.

Kill blanketweed and string algae.