Plan for big fish
Koi grow quickly and can reach two feet. A pond needs to hold them comfortably as adults. Think of volume per fish, not just the pond size today.
Depth and shape
Three feet or more is a good minimum. Steep sides discourage herons and raccoons, and a smooth bottom drains waste to the filter.
Filtration
Koi make a lot of waste. A strong mechanical stage and a large biological stage are essential. A bottom drain pulls solids to the filter and keeps the pond clean.
Oxygen
Koi need high oxygen. Waterfalls, venturi returns and air pumps all help. Aeration is vital in hot weather.
Feeding
Feed high-quality koi food in small amounts. Cool water needs a wheat-germ based food, and warm water a higher protein food. Stop feeding when the water gets cold.
Protection and health
Quarantine new fish. Watch for unusual behavior. Netting and cover keep predators away. A fish health specialist can help when needed.
Build deep and big, filter heavily and feed lightly.
