Water Gardens vs. Koi Ponds: What is the Difference?

While it can be confusing for new hobbyists to understand, koi ponds and water gardens are NOT the same thing! While both can make wonderful additions to your backyard, there are many huge differences between a typical water garden (Aquascape design water feature) and a properly designed koi pond. A water garden is primarily designed for aquatic plants, whereas a koi pond is primarily designed for koi fish (and the significant amount of waste they produce). We will discuss many of these differences below.

Pond Size

Koi fish growth is not limited by the size of their pond. Even in smaller ponds, koi fish can easily reach 2ft in length within 2-3 years. We have literally rescued jumbo size koi (over 30”) from ponds that were smaller than a standard home bathtub. While a small pond may seem okay for small koi and goldfish, clearly it is not ideal for larger koi. For this reason, pond size is extremely important. And if your goal is to provide a suitable home for koi, then bigger is always better. Many Aquascape design ponds we have seen are simply too small to provide a healthy long-term ecosystem for large koi.

Minimum Water Volume

In terms of overall pond volume, a minimum swimmable area of 1,000 gallons is recommended for a proper koi pond. Given sufficient pond filtration, a properly designed 1,000-gallon koi pond should be able to support 4-6 adult koi while still maintaining optimal water quality. Trying to stock a typical Aquascape design pond of equal size at this same level; however, is a recipe for disaster as water quality would quickly deteriorate while creating a maintenance nightmare for the pond owner.

Minimum Pond Depth

A proper koi pond should have a minimum depth of 4 feet, but deeper is always better. Most Aquascape design ponds are less than 2 feet deep, which makes them susceptible to unstable water conditions and constant environmental changes. Ambient outdoor temperature changes quickly affect these shallow ponds, which is a very bad thing for koi. To maintain optimal health, koi require a stable environment and shallow ponds do not make this possible.

Pond Design

The primary focus of the Aquascape business model is the contractors themselves, not the actual customers. “Certified” landscapers are taught how to build and install Aquascape design ponds, but they are not taught much about water quality nor how to achieve it. Much of the information shared with them regarding biology and water chemistry is also dubious at best. Words like “balance” and “natural” are commonly repeated in Aquascape sales pitches, convincing customers these glorified water gardens are somehow balanced systems that will take care of themselves. After completing literally hundreds of koi rescues from Aquascape design ponds, we can state unequivocally this claim is patently false.

Rocks and Gravel

One large koi fish can produce as much waste as hundreds of smaller koi, and virtually all this waste ultimately falls to the pond floor. In a properly designed koi pond, this waste is quickly removed via a bottom drain where it is eliminated entirely by proper koi pond filtration. In a typical Aquascape design pond, this fish waste quickly becomes mixed with the rocks and gravel covering the pond floor. This fish waste will NEVER be eliminated on its own, resulting in deteriorating water quality over time. And usually after the first year or so the pond owner must decide to either hire their “certified” landscaper to come back to drain their pond entirely and replace the rocks and gravel or purchase a pond vacuum (not cheap!) to try and clean the pond floor all on their own.

Bottom Drain: The best pond vacuum you will ever own!

We often provide pond design assistance, and we often state the best pond vacuum you can ever purchase is a pond bottom drain. In a properly designed koi pond, a bottom drain should be located at the deepest point along a smooth pond floor. Because the pond floor is not covered with rocks and gravel, fish waste and other sinking debris quickly finds it’s way to the bottom drain where it is ultimately eliminated by your pond filter. A pond bottom drain effectively sweeps your pond floor 24/7 resulting in optimal water quality, ensuring a healthy ecosystem for koi at typical stocking rates.

Sufficient Koi Pond Filtration

A sufficient filtration system is required to provide a healthy ecosystem for koi. Within a typical Aquascape design pond, filtration is provided by a skimmer filter and/or a waterfall filter. These filters typically pull water from your pond via a submersible pump hidden within the skimmer, which is located near the water surface. Because these filters alone are not sufficient for large koi, additional pressurized cannister filters are often added over time. These pressurized cannister filters are also woefully undersized for typical koi stocking rates. Since the majority of fish waste falls to the pond floor, it will never be removed through filtration and will result in deteriorating water quality over time. Based on our experience, Aquascape design ponds typically lack sufficient filtration to handle large koi fish and the waste they produce at typical stocking rates.

Maintenance Workload (Ongoing Costs)

A properly designed koi pond should provide ease of maintenance for the pond owner. Because the pond floor of Aquascape design ponds is covered with rocks and gravel, significant ongoing maintenance costs are a guaranteed. Due to deteriorating water quality, rocks and gravel must typically be removed and replaced on an annual basis at a significant expense to the pond owner. This ongoing maintenance expense does not exist for a properly designed koi pond, as the smooth pond floor assists in leading fish waste and other debris towards the bottom drain.

Final Assessment

Our assessment of Aquascape ponds and their inability to provide a healthy long-term ecosystem for large koi at typical stocking rates is based entirely on our own personal experience. Truth be told, during our travels we have yet to meet a single owner of an Aquascape pond who didn’t eventually come to wish they had made a different choice. Our goal is not to hurt any business nor brand. To the contrary, our sole mission is to find suitable new forever homes for the beautiful living jewels entrusted to our care. And for this reason alone, we strongly prefer not to make our rescued koi fish available for rehoming to Aquascape design ponds as we view them as woefully unfit for maintaining optimal koi health.