Delaware Custom Ponds LLC

The first thing we notice when coming up to view a pond is the water’s surface dimensions- length, width, and overall shape. And while it’s true that this viewing window frames the perspective and defines how the pond fits into the overall landscape, ultimately it is the pond’s depth that best reflects what we see when we look into the pond, not just at it. Also, for koi ponds in particular, depth is a key determinant for a number of critical variables that can make the difference between success and failure, as we will explore further here.

Let’s start by defining what we mean by pond depth, which for our purposes describes the average effective depth across the entire surface footprint of the pond. A serious koi pond will generally have a minimum average effective depth of 2.5 feet and go down at least 4 feet in the center, but many higher end ponds are considerably deeper.

Incorporating proper depth into your koi pond provides clear aesthetic benefits. The human eye and mind are quite good at perceiving and appreciating water depth. Shallow ponds tend to look and feel two dimensional, while deeper ponds have much greater character and presence. Add koi to the mix and the differences between a shallow and deep pond become even more pronounced. In ponds 2 feet deep or less, even medium size koi lose the ability to swim up and down, rather than just laterally, which further perpetuates the 2D vs 3D feel. If you’ve ever enjoyed watching a big koi in a deep pond shoot up vertically from the depths and breach the water’s surface to devour a pellet (or 20), you know what I mean.

Aesthetics aside, there are serious functional reasons why depth is important for a koi pond. A deeper pond is bigger, more stable, provides built-in predator protection, and as a result allows for superior koi growth, health, and longevity. Let’s start with the obvious- a deeper koi pond is a bigger koi pond. In most backyards, space is a valuable, limited resource, and the amount of ground that can be dedicated to a koi pond is finite. Depth however, is not typically limited, which means that the easiest way to add gallons is almost always to go deeper. Think about it- a 3 foot deep pond is twice as large within the same footprint as an 18 inch pond that takes up the exact same amount of space. All else equal, twice the gallons means twice the koi growth potential. Don’t be fooled, when it comes to koi and koi ponds, size matters. Anyone who says otherwise is just trying not to hurt your feelings.

Beyond size, greater pond depth means greater temperature and chemical stability. Shallow ponds are more exposed to our wildly variable air temperatures, while deeper ponds are better anchored by the more consistent ground temperature. With average intraday high and low air temperature changes in our area often reaching 20 deg F, the impact here of pond depth on water temperate stability is far from trivial. Unlike goldfish or minnows, koi are fairly sensitive to frequent temperature changes and will not grow to their potential in unstable environments. Furthermore, deeper ponds are also less impacted by serious rain events, which can often cause distress to koi in shallow ponds. Rain water is typically a lot colder and softer than existing pond water, which means that when it pours our pond water temperatures and alkalinity can both drop quickly, potentially sending koi into shock. Deeper ponds by definition have larger vertical water stacks for any given amount of surface area, which better dilutes away any given amount of surface rain and limits its negative effects on the fish.

Last but not least, let’s talk about predators. A shallow pond with significant bottom surfaces less than 2 feet deep is a gift to the herons and your pond will quickly become the most popular all you can eat buffet in town. If given the chance, koi can outswim all of the common predators in our area, and with greater depth you can stack the odds in their favor. The koi themselves are quite aware of this fact as well, and if startled or frightened will instinctively look to retreat to deeper open water. If your pond is too shallow and there isn’t enough deep open water available, even if they can avoid predation koi are likely to become chronically stressed, which has negative long term impacts on their growth and health.

As we’ve established, depth is a critical parameter for any koi pond, and a deeper koi pond is a better koi pond. That said, there are considerations that need to be taken into account when increasing pond depth. Deeper koi ponds are bigger, so they cost more to excavate, but more importantly with greater pond size you also need more powerful pumps, better filtration, more aeration, and generally speaking, more sophisticated pond designs. However, none of these additional hurdles outweigh the overwhelming benefits of greater depth, and if our purpose in owning koi ponds is to be able to enjoy big beautiful koi long term, then the choice is simple. Go deeper.