I. Risks of Complete Shutdown

1. Water Quality Deterioration
   When pumps are stopped, water becomes stagnant. Waste such as leftover feed and fish feces accumulates and decomposes slowly in low temperatures, producing toxic gases like hydrogen sulfide and methane.
2. Insufficient Oxygen
   Even though koi consume less oxygen in cold water, ice cover or prolonged stillness can cause oxygen depletion at the bottom, especially in densely stocked ponds.
3. Temperature Stratification
   Still water easily forms temperature layers (surface near air temperature, bottom slightly warmer). Koi moving between these layers may experience stress-induced "colds."
4. Inability to Handle Emergencies
   In extreme weather conditions like cold snaps or heavy snow, restarting pumps takes time to restore circulation, potentially delaying critical responses.

II. Scientific Adjustment Strategies

1. Reduce Power Instead of Turning Off
   • Set pumps to intermittent operation (e.g., run 15–30 minutes per hour).
   • Set air pumps to the lowest setting or use nano air stones for minimal aeration.
2. Adjust Equipment Placement
   • Place air stones in the middle or lower water layer to avoid drastic surface cooling.
   • Raise the water pump inlet to avoid drawing in colder bottom water.
3. Energy‑Saving Alternatives
   • Use DC variable‑frequency water pumps, which can reduce power consumption by over 50%.
   • Employ solar‑powered air pumps to supplement oxygen on sunny days.

III. Emergency Measures if Shutdown is Unavoidable

1. Immediately break ice to create ventilation holes (at least one hole per square meter of surface).
2. Add oxygen tablets (5–10 g per ton of water, effective for 6–8 hours).
3. Stop feeding and avoid disturbing the fish to minimize oxygen consumption.

IV. Precautions When Restarting

1. Check that pump impellers are not frozen and air stones are not clogged.
2. Operate at the lowest power for 1 hour, then gradually increase.
3. Add cold‑water nitrifying bacteria simultaneously to restore the filtration system.