The nitrogen cycle is an integral and vital part of the natural biological filtration system of any healthy aquatic system, helping to recycle the organic waste accumulation. Understanding the nitrogen cycle and its relation to water quality is vitally important for any koi hobbyist. Oftentimes novice keepers will ignore water quality concerns, and the resulting conditions will quickly spell harm or death for their fish.
The nitrogen cycle is a cascading process wherein each step feeds the one that follows it and each is dependent on the result of the step before it. Ammonia is converted into nitrite, nitrite is converted into nitrate, and nitrate is converted into nitrate. Without each of the main components necessary for the proper metabolic process, it is thrown out of synch and can result in fish death.
| Oxygen is a pivotal part of the nitrogen cycle in your pond, both when present and in its absence. For ammonia to be converted into nitrite (and then to nitrate), there needs to be ample oxygen for the aerobic bacteria to metabolize the byproducts. For nitrate to be converted into free nitrogen, the environment needs to low in or free of oxygen. |
Ammonia (NH3 )
This compound is the resultant chemical byproduct created when heterotrophic bacteria breaks down organic waste products. The primary source of ammonia in your pond will be waste from your koi’s digestive system. However leaves and grass, algae and uneaten food can also contribute to the ammonia levels in your pond.
Ammonia is highly toxic to all pond life in very small quantities. Your ammonia readings should be 0.00ppm,even at 0.25ppm there will be enough in your koi’s system to pose a serious threat.
CAUTION!!
Clear water does not mean clean water. Crystal clear water can still have lethal amounts of harmful ammonia or nitrite. Check your levels!
What Does Ammonia Do To My Koi?
- Disrupts water and salt regulation
- Damages gill tissue
- Slows down oxygen absorption
Symptoms of Ammonia Poisoning
- Fin clamping
- Burns to gills and fins
- Reddening of skin
- Gasping
- Isolation
How ammonia is nitrified
| Ammonia + aerobic bacteria (nitrosomonas) + O2 = NITRITE (NO2- ) |
NITRITE (NO2- )
This is the natural byproduct of ammonia. With oxygen as a side dish, the nitrosomonas bacteria uses the ammonia as a food source, creating nitrite as its waste product.
Not quite the koi killer that ammonia is, nitrite concentrations over 0.25ppm can still result in fish death.
High nitrite levels will hamper a koi’s red blood cells from absorbing and moving oxygen through the body. Known as brown-blood disease (resulting from the combination of the hemoglobin and nitrite), your koi will eventually suffocate—even in the presence of high oxygen concentrations!
How Nitrite is metabolized
| Nitrite + aerobic bacteria (nitrobacter) + O2 = NITRATE (NO3-) |
NITRATE (NO3-)
Nitrates, like nitrites, are not as harmful as free ammonia, but it is still harmful to koi in high concentrations. Anything over 60ppm is cause for concern—and a significant water change. At 120ppm it can result in fish death.
Your aquatic plants will use nitrates for their own biofunctions and so will help to leach it out of the water. Even so, water changes are a key component in helping to reduce the amount of nitrate that is left in your pond’s water and should be done routinely (depending on the water temperature and feeding schedule).
Issues that can arise from increased nitrate concentrations:
- Vein and skin damage
- Slowed healing and growth
- Depressed immune system
- Heightened chance of illness and disease
- Impeded reproduction
Organs damaged by high nitrite and nitrate concentrations:
- Liver
- Spleen
- Kidneys
- Nervous system
MAINTAINING GOOD WATER QUALITY
It is vitally important that you provide a healthy environment for your fish. Here are some tips for maintaining good water quality:
- Provide ample filtration – You must make sure that the filter system you choose for your tank or pond is sufficient to handle the amount of fish you plan on keeping. Pond installers and equipment dealers can consult with you on the proper amount of filtration for your system.
- Take it slow – When starting with a new filtration system, it takes time for the bacteria to colonize your filter media. In warm water, the bacteria will colonize in 2-3 weeks. In colder water it can take much longer. Limit the number of fish in your system, and the amount of food given to your fish during the colonization period.
- Measure your parameters – Purchase and learn how to use test kits for pH, ammonia, nitrite and nitrate. Learn what the levels of each parameter mean and how to react to levels that are too low or too high. Measure your levels frequently, particularly when starting with a new filter or new filter media.
- Limit organic waste – Your fish will produce some organic waste, there is no way around that, and waste must be present for the bacteria to colonize your filter. However, you can limit the other sources of ammonia in your pond by removing uneaten food, as well as leaves, grass and other organic material that will break down in your water.
- Clean your filter – Cleaning your filter to remove solid waste is vitally important to maintaining good water quality. Develop a routine for regularly cleaning your filter and be sure to stick to it.
As natural as the nitrogen cycle is, in a controlled environment like your pond, sometimes there is a little extra help needed to make it run smoothly. The natural biological functions of the nitrogen cycle can be regulated in a closed system (especially in a new pond) by:
- Introducing bacterial additives
- Using porous biological media with a large surface area
- Maintaining high dissolved O2 concentrations
- Controlling the fish load
- Not overfeeding
- Having a functional and well-maintained mechanical filtration
- Introducing aquatic plants
About Next Day Koi
Buying straight from some of the most reputable koi farms in the world, Next Day Koi offers some of the highest quality koi for sale at some of the best prices. Additionally, our high shipping volume means we can offer some of the most competitive rates available in the industry.
It would be great if Next Day Koi would provide an article on how to use test kits for pH, ammonia, nitrite and nitrate. BTW, Thanks for all of the information!
Your articles are awesome!! I have a koi pond, I started bringing my fish in for the winter last yr , I was hit by a mink . I use a sand filter and filter,s In the water fall , clean them twice a day. Do a backwash once or twice a week. All numbers are perfect. My one fish has a scale kind of bent upward. Not sure if I should Medicaid or salt . Or just wait and see?he is eating great everything look good on him . Salted before they came inside. Thanks for your help Jeff , if salting how long before I do a water change?
Hi Jeff, We recommend isolating and quarantining it, so that you may monitor it more closely in a more controlled environment. Adding the pond salt to it’s water that you mentioned can reduce stress and promote natural healing of the area. Also, raising the water temperature up between 75-80 degree will speed up the recovery process when coupled with the salt usage. The scale will repair itself with time or will naturally fall off. As for water changes, you will still do them as you would regularly perform them. Just add a little more salt back to maintain the percentage of salinity that you are trying to achieve. Thanks.
[…] something wrong with your water parameters. Maintaining a healthy pond requires routine water quality checks. You should test water for pH levels, as well as ammonia, nitrites, and nitrates, all […]