Why Do My Koi or Goldfish Stop Feeding?

Koi brought up in a garden fish pond are accustomed to feeding greedily because they are in a situation where they have to compete for food in a short space of time. This is quite different to the situation in the wild where carp browse leisurely looking for food throughout long periods of time.

If koi or goldfish in the pond don't eat heartily then this is an indication that something is wrong with the fish(es). This indicates a stressful environment or a sick fish which is maybe due to poor water quality.

Below are some reasons why koi and goldfish might lose their appetite.

1. Sudden changes in pond water temperature.

Koi and goldfish have a body temperature that varies with the temperature of its surroundings and their metabolism and appetite is determined by what the temperature of the water is. This means if there is a sudden very cold snap in summer then the lowering of water temperature can have a temporary effect upon the koi's feeding. In winter below about 8 degrees koi stop feeding all together in most cases.

2. The unwanted attentions of a predator such as a heron or cat

Regular visits by predator birds like herons can have a stressful impact upon koi and goldfish which can cause them to stop feeding. In this situation you should notice that the koi or goldfish become more shy and hold themselves in protected areas.

Changes in food or diet

Koi get used to a specific food ... its smell and taste and if this is changed it may take a while before the fish starts feeding again. Rest assured if this is the case feeding will restart fairly soon.

Water Quality

Water quality is such an important variable in any artificial pond that poor water quality will have a number of negative impacts upon a fish's behaviour one of which may show as lack of appetite.

By carefully looking after the biofilter and testing for ammonia and nitrites this effect can be discounted.

Sick Koi are likely to stop feeding

Sick koi tend to stop eating. As well as stopping feeding the fish will start to show other symptoms associated with the relevant disease the fish is suffering from.

A very useful procedure is to take a mucus scrape and examine the sample under a microscope to view any likely parasites. If there are large numbers of parasites such as Trichodina, Gyrodactylus, Chilodinella etc visible then this is the likely cause of loss of appetite, and can be treated accordingly. This, however, is not completely satisfactory as it is best practice to identify the likely cause of the koi becoming more susceptible to disease in the first place, being able to prevent it from happening again having cured it.

You can download my free koi food calculator to use to work out what you can save by using the right food type.

Please also check out this UK Pond Doctor site

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