Minimum Pond Depth
Pond must be at least 90cm deep to prevent freezing solid. Goldfish hibernate at the bottom where water stays at 4°C even under thick ice.
Shallow ponds (under 60cm) are death traps — either freeze through or oxygen becomes insufficient.
Keep an Ice Hole Open
Never smash ice — the shockwave can kill fish. Use a pond de-icer or floating air stone to keep a small hole open for gas exchange.
A sealed frozen pond traps CO2 and methane from decomposing debris. Fish suffocate within 3-4 weeks.
Pre-Winter Preparation
Stop feeding when water drops below 10°C — goldfish cannot digest at low temps. Uneaten food rots and pollutes during hibernation.
Remove leaves and debris from pond before freeze. Trim back dying plants. Clean filter but leave established biology intact.
Spring Awakening
When water reaches 10°C, resume feeding with easy-digest foods like wheat germ pellets. Increase portions gradually over 2-3 weeks.
Watch for ulcer disease that appears after winter stress. Inspect each fish for sores and treat individually.