The core reason for pausing feeding on summer afternoons is to avoid the risks of digestive crisis and water quality deterioration caused by high temperatures. During the afternoon period (typically 11:00 AM to 3:00 PM), when sunlight is strongest and water temperatures are highest, koi face multiple physiological risks:
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Sharply Reduced Digestive EfficiencyWhen water temperatures exceed 30°C, the activity of digestive enzymes in koi significantly decreases, and intestinal motility slows down, prolonging the retention time of food in the body. If feeding occurs at this time, inadequately digested feed can easily ferment abnormally in the intestines, producing large amounts of gas and toxins, directly causing enteritis, bloating, or even intestinal blockage.
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Critical Imbalance Between Oxygen Supply and DemandHigh afternoon temperatures directly reduce the dissolved oxygen saturation in water, while the respiration of algae and microorganisms further depletes oxygen. At the same time, koi require more oxygen for their own metabolism. Adding feed increases oxygen consumption for digestion, making koi highly prone to surfacing due to oxygen deficiency, which in severe cases can lead to suffocation and death.
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Dramatically Increased Risk of Water Quality DeteriorationUneaten feed decomposes at twice the normal rate in high temperatures, rapidly releasing toxic substances such as ammonia and nitrite. Moreover, nitrifying bacteria activity is also suppressed by the heat during the afternoon, reducing toxin breakdown capacity. This can quickly lead to acutely toxic water conditions.
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Aggravated Stress Response in KoiHigh temperatures alone place koi in a state of heat stress. Feeding at this time adds additional metabolic burden, weakens immunity, and increases the risk of secondary infections (e.g., red skin disease) or parasite outbreaks.
Scientific Alternatives:
Concentrate feeding during cooler periods (early morning 5:00–8:00 AM and evening 6:00–8:00 PM), prioritizing easily digestible, low-protein feed. If koi exhibit foraging behavior in the afternoon, minimal amounts of fresh fruits or vegetables (e.g., watermelon rind, cucumber slices) can be offered as a cooling supplement, but any leftovers must be removed within 10 minutes. Additionally, enhance aeration and shading measures in the afternoon, and avoid disturbing the fish.
In summary, pausing feeding in the afternoon is not merely a simple act of "skipping a meal" but a proactive protection strategy based on koi physiology and aquatic environmental changes. It embodies the wisdom of "retreating to advance" in health management.
