Winter feeding of pond fish and koi

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Once temperature drops to about 50 degrees F or 8 degrees C fish will stop feeding

Ponds and Feeding in Winter

Here I am talking about South African, Australian, Florida or other similar winters and not North American or European winters.

Biofiltration processes slow down at lower temperatures. This is of course true but a few more comments are worthwhile.

In winter in Johannesburg and other highveld areas nighttime temperatures fall dramatically and as we all know swimming becomes impossible.

In ponds and especially large and deep ponds temperatures can fall to and remain at temperatures around 8 degrees centigrade (46 degrees Fahrenheit) for short periods of time. In these ponds you will notice perhaps that fish tend to go to the bottom and remain there motionless. This is the sign to definitely STOP feeding but I will come back to this point later.


With regards to filtration it is still possible for a biofilter to be commissioned but it will take longer to mature. This means high doses of ammonia will take longer to get under control using even a mature filter. The important points to bear in mind therefore is if temperatures are low are

  • feed less and

  • preferably feed earlier in the day while water is warmer giving the fish time to digest the food.

  • In this way the load on a biofilter is reduced anyway.

  • As far as a new filter is concerned put less fish in than you might under summer conditions.

Now lets talk about winter-feeding. This is a subject allowing for great debate and a degree of common sense is required to participate in the debate.

Point 1 - there is a school of thought that says stop feeding your koi when temperature reaches 10 degrees Centigrade (50 degrees Fahrenheit). This rule is responsible for many fish deaths - the fish might not die in winter but they die in spring when general pond activity picks up.


Point 2 - imagine your being denied food in winter when you were hungry and moving around. Come Spring you would not be in good condition. If you are in poor condition you become susceptible to all sorts of disease. One reason why HIV is deadly in humans.

The truth is as follows:

If your fish are swimming around they are hungry and need sustenance. Sure they need much less food but they need it and make no doubts about this. Fish are clever - they do not waste energy and move only in search of food. When food is no longer important they lie motionless on the bottom - almost hibernating to conserve energy.

Of course there is a lot of technology and science in a pond environment and exploitation of this science allows koi to be well looked after, live for a long time and grow large.

Most koi keepers however have limited funds to implement technological solutions (like heating a pond in winter to maintain 15 degree Centigrade temperatures or 60 degrees Fahrenheit) and just want to enjoy their pond. This is where common sense plays an important role.

Common sense should always be a test of any "rule" particularly when this "rule" is passed from mouth to mouth to the extent it almost becomes dogma.

Therefore feed your fish small amounts if they are swimming around.

What is critical is the quality of food at low temperatures.

The food must have easily digestible protein sources and all correct vitamins and trace elements - wheat germ is the common and often-recommended source of this type of protein but this food lacks almost everything else the fish requires.

So apply the common sense rule. Is it better to feed wheat germ or a balanced food that contains highly digestible proteins AND trace elements AND vitamins or is it better to supply wheat germ? Dealers make more money out of selling wheat germ in addition to normal food.

So how do you now if the proteins are highly digestible? - the one quick test is to read the ash level on the food label. If more than 5% ash then the protein source is suspect - good protein sources do not have a lot of ash in them.

Ash is an indication of the fact that low grade raw materials are used - bones, scales, inorganic fillers etc all of which show up as ash in the final food. If a food does not supply reliable analysis figures on the label DO NOT BUY THE FOOD. Also ask the dealer questions about the analysis.

By the way ash and moisture add nothing to the food and are a waste of money - unfortunately it is impossible to avoid ash and moisture altogether.

Consequently if a 5 kg bag of food contains 12% moisture and 13% ash then 25% (a whopping 1.25kg) of what you bought is just going to pollute the filter since it will come straight out of the rear end of the fish.

This is what I mean by a common sense approach to pond keeping and saving money and improving your system.

Have you ever noticed the large amount of faeces on the bottom of your pond? This is mainly ash from low quality food.

If you want to cross reference this point compare what you see on your lawn if you feed your dog a common dry dog food as against what you see when you feed one of those more expensive foods you only find at the vet. You will see much less mess. Your dog will also eat less kgs and will be in better condition. Makes sense to me.

In the same way a food containing 35% protein contains 40% more sustenance than one containing 25% protein. This is a major difference and not just in value. Koi need high protein levels to develop well.

Ask yourself a simple question. What is the point of spending good money on ponds, filters, pumps, koi and then trying to save a few $ on food? In any case a fish needs a certain amount of protein. A fish will need far less food of 35% protein than it will of one containing 25% protein - in fact 40% less. At the end of day the total food bill will be the same although good quality food may cost more per kg.
This web page is an extract from Tony Roocroft's "The Complete Pond Solver" ... you can read more about it at ... when you buy the book you get 12 Excel pond calculators free as well as "Water Lilies and Pond Aquatics" ebook also free.