Understanding the Biological Cycle of Your Koi Pond

The biological cycle is really better defined as the “nitrogen cycle” because primarily what pond keepers are concerned with is nitrogenous waste.  When it comes to elements, nitrogen is pretty common. In fact, it makes up almost 80% of our atmosphere so it’s not surprising that it should be found in many plants and animals, too. Nitrogen can be found in proteins and DNA as well as fish waste. The nitrogen cycle in your pond really has to do with what happens to the nitrogen in fish waste, decaying plant matter and uneaten food. The following is a step-by-step explanation of that process.

1. In your pond fish excrete waste and maybe your koi munch the stalk off a submerged plant so it lies decaying on the bottom and there happens to be some uneaten food mixed in with everything else. These are not your only source of nitrogenous waste but they probably make up a large proportion of it. The first nitrogen-based chemical that will appear in your pond is ammonia. This comes about because bacteria and some fungi will subsequently assimilate or break down the aforementioned “stuff” lying on the bottom of your pond -the by-product of which is ammonia. On the scale of harmful chemicals to your koi ammonia is number one.

2. In a koi pond with a good biological filtration system there will be nitrosomonas bacteria and these guys will take ammonia and oxygen and use it as fuel and turn it into a waste product called nitrite. On the scale of harmful chemicals to your koi nitrite comes in at number 2.

3. The next helpful bacteria in the cycle are called nitrobacter. These bacteria convert nitrites and oxygen into a waste product called nitrate.
4. The nitrates are then assimilated by another suite of bacteria that do not use oxygen, these are called “anaerobic bacteria”. They live in oxygen free parts of the pond and produce free nitrogen from nitrates.

nitrogen cycle

Basic Nitrogen Cycle of a Koi Pond

Filter systems were discussed here but where do aquatic plants come into play? Plants, like submerged vegetation and surface vegetation (lilies), are critical parts of your pond’s ecosystem for their abilities to “suck up” nitrates, produce dissolved oxygen and block the sunlight that would otherwise help algae grow. So what is so bad about algae? Algae is good on one hand because it produces dissolved oxygen which enters the water but algae also grow rapidly then die and once that happens you will end up with a lot of decaying algae in your pond. All the dead algae will drive up ammonia levels and lower oxygen levels. Remember those nitrosomonas bacteria that use oxygen and ammonia to produce nitrites? The more decaying material, the more oxygen will be used up by bacteria leaving your pond with decreasing levels of dissolved oxygen.

If you would like to know more about water chemistry and how it affects your koi please see my article here.

I’ve got koi fry –now what!? A step wise approach to raising baby koi

If you just noticed that your pond now has a million little koi fry swimming around then skip down to the feeding section but if you haven’t bred koi yet and need an introduction then read on. Spawning typically occurs in the early summer months and is very water temperature dependent – 68 degrees FContinue Reading

What are the ideal water conditions for healthy koi?

There will certainly be a lot of differing opinions on the best water conditions for koi but one thing remains constant: poor water quality leads to a host of other health problems that are certainly avoidable with proper care.  Because stress originates from poor water quality, follow these guidelines for healthy water and healthy koi.Continue Reading

The Major Koi Varieties and Their Traits

Presented here are what many consider the 13 major varieties of koi or “Nishikigoi”.  There are certainly some koi practitioners that may consider there to be up to 16 varieties (and even up to 22 if one counts newer strains of koi).  This summary includes some history of the variety (where applicable) as well asContinue Reading

Aquatic Plants for Your Koi Pond: Why They’re Important and How to Choose the Right Ones

Adding plant life to a koi pond helps improve pond life for koi, as well as adding beauty to the pond itself. Koi owners need to make sure they select the right aquatic plants that will harmoniously co-exist with their koi. They also need to ensure that their plant placement is done properly as wellContinue Reading

Top 5 Most Common Koi Pond Problems and Their Solutions

Having a Koi pond can not only increase the visual appeal of a property, but it can also aid in developing a passion for an environment that you are able to maintain for yourself.  Koi ponds can certainly encounter a number of issues throughout time, especially considering the amount of time and effort that oneContinue Reading

Selecting Food for Your Koi

Koi are omnivores, which means that they consume both plant and animal matter. In fact, they often prefer eating aquatic larvae and insects. Koi fish make incredibly beautiful pets—though they’re also incredibly voracious fish. These elegantly decorated fish actually devour nearly anything that finds its way into their water. Since koi fish eat practically anything,Continue Reading

How to Breed Koi for Profit

  It’s not as crazy as you might think to breed Koi fish for profit, as thousands around the world have done with great success. Knowing how to do it, though, is another matter altogether; let’s review exactly what you need to do in order to breed Koi fish for profit and turn a veryContinue Reading

Koi Diseases and Their Treatments

    For a koi, life can be full of peril.  The fish in an outdoor pond are subject to not only birds of prey and raccoons but to things you often can’t see that live in your water and infect your fish.  Fortunately, there is a great deal of information on koi diseases andContinue Reading

Top 15 Reasons to Have Koi and a Koi Pond

  Enjoying Koi pond in your backyard not only provides a charming attraction to your visitors, but it’s also a great way to relax and rejuvenate at your home. There is something wonderful about enjoying the elegant view of fish and water along with hearing relaxing and tranquil sounds of the water. Many of usContinue Reading

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