There is no definite answer to that question as most constructed pond owners have and expect something different from their respective ponds. Also, most ponds are built with varying depths. When it comes to wintering fish, in the New Jersey area and most other parts of the country, a depth of 18” should allow the pond owner a worry free winter season keeping their fish outdoors, however the FULL SERVICE AQUATICS typical installations go to a depth of 24” – 30”. At this depth range our customers have NO problems keeping their fish outdoors for all seasons. For water gardening purposes depths of 6”, for shallow water plants, to 24” for deeper water plants will suit most water gardeners just fine, also allowing the hardier plants to winter over outdoors without any problems. Something to consider… most municipalities will consider a body of water 36” or greater in depth, regardless of length and width dimensions, an insurance liability; and will require permits, insurance, and fencing to be installed with the pond even though it is not used for human immersion or recreational purposes.