Frisky Koi And Limiting Overproduction

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On the one hand, it’s great to have happy and healthy fish. This is as it should be if you’re doing a good job at managing your Koi pond. On the other hand, happy and healthy fish are usually really good at making more fish. Or maybe it’s the other way around.

Anyway, this can often pose a bit of a problem for the pond owner.

We know that too many fish in a small pond will cause issues that are very common. Algae, in any form, and this means green water, string algae, hair algae, you name it, will likely appear because of high nutrient loading in the water from the fish waste. If these same nutrients end up getting so high that the natural cleaning and balancing mechanisms in the pond can’t keep up, you could end up seeing an ammonia spike, and this can be deadly for the fish. Neither of these issues are something you really want to deal with.

Now to be honest, in the short term there are some things you can do if you’re running near the limit on fish loading. Obviously you need to make sure your filtration is working well, and you must make sure your beneficial bacteria counts are equal to the task of neutralizing the nitrites and nitrites that the fish waste produces. You can add some good plants…I know, I say this all the time, but plants are natural filters and you need all the help you can get. And yes, if you read last weeks article you’d know that you can have Koi and plants together much of the time.

Ultimately though, everything has it’s limits, and such is the case with this balancing act in your pond.

How Many Koi Is Too Many?

So, how many fish are too many for a particular pond? It’s a good question and one that every fish pond owner should know. We have a pond calculator here that will help. It’s the second tabulation tool down on the page and here you’ll put in the total gallon size of your pond, click the magic button and it will tell you just how many “fish inches” your pond can handle.

Keep in mind this is a very general rule and many things vary, most notably the quality of your filter package, but all in all, if you have algae issues, and you have fish, they should be on the suspect list to look at in more depth.

It needs to be kept in mind that Koi don’t simply grow to fit into a particular pond. There are numerous examples of really big fish growing several feet, yet the pond owner had them in a really small pond or tank. Growth is pretty much dictated by genetics and in some ways the quality and quantity of food which affects the rate of growth but all in all, the pond size won’t have much to do with it.

So what do you do if you find you have too many fish in a pond for it’s size?

Population Control For Koi

OK so now we come to the really tough part of this story. You’ve got too many fish and that’s causing major algae and water quality issues in the pond. What can you do?

Probably the first and most direct step is to reduce the number of fish in the pond by finding some good homes for a few of them. Now this doesn’t mean taking them down to a nearby pond or community watering hole and letting them go. No, the proper thing to do is to find another pond owner that’s perhaps just starting out, or looking to add some quality fish to the pond and talk with about your fish. This is why it’s such a good idea to connect with other pond owners in your area or koi clubs, etc because of the contacts you can make.

Without a doubt the “find-a-home” routine is kind of reactive but there are times when you’ll need to do it.

There is a more proactive thing you can do and I bring this up as an option to try. Some of you may not be comfortable in doing it, but it does work for population management with koi. It also came as a challenge of sorts that if I could suggest a reasonable way to keep koi from producing so many darned young, then I’ll get fish named after me and who wouldn’t want that!

All kidding aside, we need to get down to the serious business of curbing an exploding population of breeding fish. The best way to do this, although it’s not pretty necessarily, is to use nature’s processes to do the job.

At any point where you notice that spawning is underway, stop feeding your fish completely. You may need to go several weeks through the process but koi, when hungry enough, will turn to “natural foods” if you will. They’re not cannibals but they will eat eggs and very small fry as they probably confuse them with insects. Without supplemental food these things would be part of their natural diet and so it’s not a stretch to use them to help manage an over-productive pond situation. But once the baby koi start to clearly resemble fish, the adults will probably leave them alone so this entire process must be timed properly in order to be effective.

Again, I’ll stress that this may not be something everyone is comfortable in doing. But it is an option and using your own best judgement it may help you maintain a more balanced, healthy, and fish friendly pond.

For additional information on managing your koi population be sure to visit

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