Keeping koi fish, like taking on the care of any animal, is a big commitment.
You are committing to take care of those animals for their lifespan, which for koi fish works out to be between twenty-five and thirty-five years. Needless to say, adopting koi is a pretty big deal due to this alone.
Still, koi fish are very healthy and easy to take care of despite growing to be large sizes so it sort of balances out.
Part of the commitment, though, is that due to their size, they also need a lot of space. Let’s take a look at koi pond size minimums and learn about keeping koi in a small pond.
The Minimum Requirements
With adult koi fish, the minimum pond size requirement is around 1,500 gallons and three feet deep.
This may sound like a lot but when you consider how much water 1,500 gallons actually is, it does not equate to much space at all at a three feet depth.
Koi fish need this depth since they are larger and their movements can sometimes make them prone to flopping out of shallower water features, resulting in them injuring themselves or even dying if not found soon enough. They are also more likely to be preyed upon by birds, raccoons, and other native animals, as well, if they are not at a depth that the animals cannot reach them.
Following along with the same idea, there should be a gap between the surface of the water and the rim of the pond.
This is because predators like raccoons can wait at the edge of the water for a koi to swim by and snatch it up to make a nice, tasty dinner. Larger birds can also stand in the water and grab the fish with their beaks if it is too shallow, as well.
Having a lot of plants that sit on the surface of the water can make a difference in this risk factor, as well, as the koi have a place to hide from the predatory fish, as well.
Some people even put in devices like bamboo deer scares to spook away predators, too, as an extra layer of protection.
These are the bare minimums to keep your fish safe on a physical level.
Now that we understand these requirements, let’s take a look at how to keep your koi safe in smaller ponds on a chemical level, too.
The Minimum Chemical Requirements
When looking at your pond, you probably notice that, though it is large enough, it is missing a few things.
When setting up a koi pond, you must have adequate filtration and oxygenation in order to support life.
To do this in an aesthetically pleasing way, many people use a hidden pump filter for filtration and add-in an aquatic movement area to help with aeration instead of adding in an oxygen stone or other piece that requires tubing that would be visible and break up the naturalistic appearance of the pond.
To do this, most people use something like a waterfall or small fountain feature to create the necessary movement to prevent the water from becoming stagnant.
These are also aesthetically pleasing and look stunning, especially if they are well-matched to other facets of the pond’s designs. Rock waterfalls are popular right now, as they are easy to match to the rest of the pond and make look natural.
Similarly, many people add small fountains to the center of their pond or arcing sprayers to the edges to create the necessary movement without detracting from the simplistic design of the pond or other features.
How Many Koi Can a 1,500 Gallon Pond Hold?
If you go the absolute minimum route with your pond, you obviously cannot have a ton of fish.
Overstocking your pond is one of the biggest mistakes you could make, as it will result in the fish not being able to move easily, cause fighting, and allow diseases to spread more easily. Plus, fish are more likely to injure themselves or others in ponds that are overstocked.
A pond like this can hold around five adult fish. Even if you buy them as small babies, they will not stay small for long.
Some koi can reach two feet in length within a matter of just a few years, making ponds that are smaller already not adequate if overstocked. This means you should err on the side of caution and not exceed this amount when choosing your fish, even if they are babies or fry.
For jumbo koi or bigger varieties like butterfly koi or ghost koi, you may want to opt for even less, sticking to three koi, unless you are planning to expand your pond within the foreseeable future.
Koi ponds can easily be added onto and most koi prefer more space than a 1,500 gallon can provide anyways, so do not hesitate to dream big and have a plan for expansion once your fish reach adulthood even if they are small right now.
If you plan to mix goldfish and koi, stick to the same guideline, as though goldfish typically are smaller than koi fish, they are very high waste, meaning they put a lot of strain on the natural bacteria and environmental factors of the pond.
This can make it hard to keep the water clean and even post a health risk to all of the fish in the pond if this issue is not remedied by expanding the pond or removing some of the goldfish.
It is better to understock a pond than overstock it, as you can always add more later but once the bacterial content or other factors of the pond are thrown off, it can be a pain to get them back to normal.
Think of The Growth Rate
When choosing your pond size, it is best to consider the growth rate and size potential of your koi fish. If you do this, you will likely be just fine!
Good luck and remember, with koi pond volume, bigger is better!