Koi fish

Keeping Koi in the Northeast

We’ve had a koi pond for almost 20 years.  It was a “present” from my husband for my birthday.  I wanted a pond, and he got busy with the backhoe….and we ended up with nearly a 5000 gallon hole in the ground.  A bit larger than he intended.

I love hearing the water run over the water falls. We don’t have any stream nearby, and I grew up with a creek running nearly a farmhouse, so it’s a lovely homey feeling for me.

Keeping a koi pond is not work free.  This is not a natural pond, and it relies on us to keep it running. The filter must be cleaned regularly, and it’s no fun when a pump dies out in the middle of winter.  The pond itself needs to be cleaned up so leaves, sticks and other debris don’t rot in the water or clog the filter.  Algae seems to take over in early spring.  And the fish have to be fed, just like any other livestock.

There are plenty of books about Building a pond and keeping koi for reference.  If I had to do it again I probably would have talked to actual koi pond owners rather than just garden centers who build and sell koi.

This year I ended up finding large bags of koi food on Amazon, and signed up for a monthly automatic delivery.  No more forgetting to have it on hand or running to the store to pay a premium price for a small bag until my order could arrive.  It’s been great.

Butterfly Koi

Black and gold Butterfly Koi, keeping a koi pond


The most asked question is: What do they do in the winder. The answer: they sleep. Koi hibernate. They settle to the bottom of the pond (ours is about 3 feet deep) and stop swimming around. They don’t eat.

In spring everything around the pond wakes up.  Plants start emerging from the pot over-wintering in the water.  Frogs wake up and the spring croaking begins.  It’s always a treat to go out on an early spring night with a flashlight to see if the bulls frogs have emerged.  Dragonfly’s appear.  Garter snakes come to visit to look for a meal of bugs,  small frogs or tadpoles.

Koi are active once the water temperature is up above 40 degrees F, and the warmer the water gets, the move they move around and eat. Once the temperature gets to 55- 60 degrees they will spawn. Usually this is accompanied by a lot of splashing water, torn up plants and not eating for a day or two.

During the middle of summer, the hotter the water gets, the lower the oxygen saturation. This means fish may not have enough oxygen to meet their body needs. We usually put in a couple  lines with bubble stones to aerate the water and raise the oxygen level.  If they struggle it’s obvious – they come to the surface and try to gulp air with their mouths.

Like any other livestock, there are predators.  A Great Blue heron can wipe out a dozen or more small fish if it wades around the edge.  In this case some fishing line strung around will prevent them from landing and wading.  Also some hawks and owls will prey on fish.  Most of our are quite large now (a good 5 pounds or more), so they may be injured with talons or beaks, but not likely to be actually taken from the pond.

The bears are a different story.  We woke up one morning to find only  about a foot of water left in the pond.  A bear had gotten into it overnight, and left behind big gashes in the liner, and all the water just seeped out under the water level got below the tears.  We also found fish carcasses here and there under bushes and trees where he or she fed.  We fenced in the yard with stock fencing, which has been a fairly good deterrent.   And this year, right after a young bear climbed over the fence and went for a swim, we put up an electric fence around the yard, secured to the tops of existing fence posts.  So far, so good.

In autumn, we put the pond to bed.  Netting covers it to keep out the falling leaves. all the plants get cut back.  One final good cleaning of the biological filter so it can just circulate water all winter. Frogs and fish hunker in the bottom. No more feeding them until spring.

I find the pond very relaxing – I love the sound of the water, and watching the fish swim about is a great stress reducer.  The actual cleaning of the pond is mindless work, something I can do when I don’t want to have to think anymore.  That’s the trade off for the work of keeping koi.

What do you have in your yard or house to reduce stress? that you love to watch?