Tropical Fish Central

I have long been fond of the color, beauty and elegance of Koi ponds.  When I moved to my new house a few years back, I included building a koi pond in the a project to landscape my new back yard.

The first thing to consider when starting out with koi is the habitat.  Koi grow very large – much larger than most people will realize.  This video, from  youtube, gives the best sense of the real size koi grow to that I’ve seen:

Koi can grow to 3 feet long (just under 1 meter), as you can see in the video above. These fish require large volumes of water to live a healthy life. The general rule of thumb is 1000 gallons of water for the first koi, and 200 to 500 gallons per each additional fish. This makes koi too large for nearly all aquarium tanks – and inappropriate for residential aquariums. Koi do well in outdoor ponds, even during winter. Koi are cold water fish, and can survive in freezing temperatures, so long as the water is not permitted to completely freeze over. This need drives an important, but often ignored dimension of koi ponds – depth. For most climates, 4 to 5 feet deep is sufficient to keep water from freezing. A pond this deep will also help protect koi from predators – birds, raccoons, and the like.

The next important requirement for koi ponds is water circulation. Either a waterfall or a sprayer will do, but the important thing is to keep the water moving.

So far, these suggestions have been pretty standard and not surprising, but here are three more that have saved me a lot of problems:

1. Growing plants in the pond will absorb toxins from the water, such as nitrate. They also look very nice, too.  Here is a picture of a flower from one of the plants growing in my pond:

2. My next trick is using a UV light in the filter/pump box.   UV filters kill microbes, including algae, parasites, bacteria and viruses.  UV lights will often get rid of brown or green murky water, which is caused by algae blooms.  Of course, this will almost certainly lead to an abundance of some other type of algae, such as slime algae, unless there are plants to out compete such algae.  UV filters also serve to minimize infection from bacteria, viruses, or parasites, such as ich, which find their way into the pond.

3. My final suggestion is minnows.  I keep a stock of about 50 rosy red minnows in my 3000 gallon pond.  They add some life to the pond, but they serve a much more important purpose – they are sacrificial fish for birds and other predators.  The minnows are brightly colored and generally swim at the top of the water, and so are easy targets for such predators, leaving the koi alone.  Minnows are available at Petsmart near me, for about $0.12 each.  I will generally need to restock minnows once or twice during  the summer.

Now for a special treat: the Koi Pearl

Note that I do not have one, and have never seen one in person, but they sure do look cool!