The Depth Of Your Pond Should Be Determined By If You Want Plants And Fish, Space And If You Plan To Hire A Professional Maintenance Co. Or DIY. One of the most important decisions you can make about your pond is the depth. If you plan on having fish or aquatic plants, you need to have a deeper pond area to accommodate growth, ample living space or, in the case of certain plants, if they need less sunlight to thrive. For Koi ponds, you should have at least 3 feet of depth or more to not only supply them enough room but to have a larger volume of water to combat any polluting effects on the pond that the fish may trigger. Some ponds need to be a bit deeper so fish have a chance to hibernate in winter. Research the types of plants and fish you would like, if any, and follow the recommendations for a healthy volume of water they need to thrive in. Another factor to the depth of your pond comes down to the issue of maintenance. In general, larger ponds ...