Second after knowing your budget choose a pond location. The best site is near to your home it shuld have electical connection, water adn sewage. It shuld stay away from predators like hawks, heron, cats, foxes and their likes. Always avoid pond under over hanging branches of trees as these may extrude toxic substances into the water and leaves will pollute the water. Also their roots might seek make damage on the pond which causes it to leak.
Third choose the size and depth to your pond make sure not too big for your garden and not to small for your intended number of kois.
Fourth the pond material you want to use but the best of its kind is far more recommended.
