The Aquarium Nitrogen Cycle – Is Your Tank Using It Yet?

Written by Dennis

The Aquarium Nitrogen Cycle is the single most important thing that all beginner aquarists must know before establishing their tanks.

I don’t want to scare you, but it’s true that an improper cycling of the tank may lead to deaths of fishes. So, if you want to keep your pets healthy and lively then pay close attention to the entire post.

What Is Fish Tank Cycling?  aka  Aquarium Nitrogen Cycle 

The nitrogen cycle is a common phenomenon in our nature.

The waste products produced by the living beings have a high level of toxins like Ammonia (NH3), Nitrite (NO2), and Nitrate (NO3), which all are nitrogen compounds. These toxins are eliminated by beneficial microscopic bugs known as bacteria and the process is called as the nitrogen cycle.

Clearly, removing the toxins makes nature a healthy place to live for the living beings. Same goes for the aquarium. The nitrogen cycle occurs in the fish tank, helps fishes to live a stress-free and healthy life.

Steps Of Fish Tank Nitrogen Cycle:

  • Fish and Plant Wastes produce ammonia.
  • Ammonia gets turned into Nitrite (NO2).
  • Nitrite transforms into Nitrate (NO3).

Aquarium-Nitrogen Cycle 600

Why Implementing Nitrogen Cycle Is Essential In A Fish Tank?

If the nitrogen cycle is a common phenomenon and takes place in nature every day, then why you must need to implement it in the aquarium? It should be a spontaneous process, right?

No, not in every case. As aquariums are tiny forms of the large water bodies, the number of waste products can easily spike and create health issues for your fishes. While in large water bodies, the waste products flow away or easily mitigated by beneficial bacteria colonies.

In a fish tank, you need to initiate the nitrogen cycle and supervise it, until it runs fine.

How Long Does The Nitrogen Cycle Take In An Aquarium?

As the aquarium nitrogen cycle needs to be implemented with care, it may take from 2 – 8 weeks. Each of the stages is a little time-consuming, but once the nitrogen cycle starts to work properly, the time will worth the health of your fishes.

Stages Of The Aquarium Nitrogen Cycle: 

Every nitrogen cycle in the aquarium has 3 stages.

Stage 1:

The fish and plant waste products or the leftover foods are broken down into either ionized ammonium (NH4) or unionized ammonia (NH3). Ammonium is not at all harmful for fishes, but ammonia has a toxic effect on aquatic lives, so if the waste materials get transformed into ammonia, you need to eliminate it soon.

The pH of the tank water highly determines whether ammonium or ammonia is going to release. If the pH is below 7 then you will have ammonium, if the pH is equal to or greater than 7 then ammonia will get released in the tank.

Any amount of ammonia is bad, although 2 ppm suggests your fishes are in grave danger.  After adding the fishes in the tank, from the third day onward ammonia will start to rise.

Stage 2: 

The Nitrosomonas bacteria in your tank will oxidize ammonia, and eliminate it. As byproducts, you will get nitrites which are also toxins and you need to get rid of them real soon. So, now we don’t have ammonia, but we have to deal with nitrites which usually get released at the end of the week after introducing the fishes in the tank.

Stage 3: 

In this final stage, the Nitrobacter bacteria will convert the nitrites into nitrates. Although nitrates are not as toxic as the ammonia and nitrites, a large amount of nitrate needs to be eliminated from the tank to keep the fishes in good health. Established tanks need to be tested for nitrate levels every week to ensure better health for the fishes.

How To Fix Nitrate Levels In Fish Tank? 

If not present in an enormous amount, the end product of the aquarium nitrogen cycle, will not be harmful to fishes. Also, not all fishes will get affected by nitrates, rather only a few types of them. But excessive amount of nitrate can increase the growth of algae, which will be unsuitable for fishes.

To decrease the amount of NO3, the best you can do is to change 25 – 30% of the water every week. Other than that if you have some live plants in the aquarium, then the nitrates level will be adjusted soon as nitrates work as nutrients for the plants.

Although, nitrogen cycle for freshwater aquarium is more or less same with the marine tanks, in saltwater fish tanks nitrate can be broken down differently. The live rocks and deep sand beds usually have anaerobic areas, where denitrifying bacteria break down nitrates into suitable nitrogen (N2) gas that gets evaporated from the surface of the fish tank.

You might be interested in knowing:

How To Cycle A New Aquarium? 

Now, if you have bought a fish tank recently, then cycling it, is as essential as feeding the fishes. Also, Cycling an aquarium properly is not that difficult but needs patience due to the time it will take to establish an effective nitrogen cycle for an aquarium. It is better to use a separate fish bowl to keep the fishes during the cycle setup.

Although many aquarists usually use the traditional method to establish nitrogen cycle with fish, I have found that for beginners, this method will be a bit difficult as they do not have much experience. If you want to use the traditional method, then make sure to have the aquarium test kit handy for better results.

Cycling Fish Tank Without Fish

Cycling new aquariums without fish is the best way to create the proper housing for the fishes. It also takes less time than the cycling process with fish. Here are some effective ways to start your aquarium nitrogen cycle.

  • Using Fish Food:

Just set up the tank, and use all the necessary accessories like a filter, lighting, pump etc., but do not put fishes into the tank. Instead, drop in few flakes or other types of fish foods every 12 hours. The food will decompose and ammonia will get released. Now use the aquarium test strips to measure the amount of ammonia, nitrite, and nitrate for the upcoming 2 – 6 weeks, to ensure if the nitrogen cycle in fish tank working properly.

  • Using Raw Fish And Shrimp:

You can drop big pieces of raw fish and shrimp in the tank every alternative day. As the meat decomposes ammonia will get released. And slowly the aquarium nitrogen cycle will start to work. Again the aquarium test kit will come handy.

  • Adding Pure Ammonia or Ammonium Chloride: 

You can use 5 drops of ammonia in every 10 gallons of water or if needed you can add more drops until your test kit catches it up. But make sure to note the number of drops because you have to repeat it daily until you see the nitrate reading.

Once your test kit starts to indicate the nitrite levels, you can cut the number of drops into half to maintain the nitrogen cycle properly.

Ammonium Chloride solutions can also be used to initiate the nitrogen cycle. 4 drops of that solution per gallon will give you faster establishment of nitrogen cycle or the freshwater aquarium bacteria.

  • Using Gravels Or Filter Media From An Old Tank:

It is the most effective way to establish nitrogen cycle in your new tank. As the old and established tanks have colonies of beneficial bacteria in their filter media, using them at least for 3 weeks to filter your new tank water will give you proper cycling of the tank.

Do not forget to feed the tank very often. The decomposed waste will release ammonia and the beneficial bacteria will oxidize it and transform the nitrites later into nitrates. You will be surprised to see that your test kit will catch up nitrite reading in a day or two.

Although the process is very fast, it has one downfall. If the previous tank has been medicated with copper, then it will not be preferable for invertebrates. In case, you are not planning to have any invertebrate then go for that filter media and establish the nitrogen cycle in your aquarium.

  • Using A Live Rock For Cycling:

Live rocks are the most suitable for cycling saltwater tanks. These rocks are wreckages that have broken off a coral reef structure due to any natural cause, for instance, hurricanes and tropical storms.

These are called ‘live’ because on coral reefs several living organisms like marine worms, algae, small crabs, bacteria, small crustaceans are found. So when a piece of coral reef breaks off, some of those organisms come with it.

As the live rocks are tremendously porous, many aerobic and anaerobic bacteria get enough surface area to live on it. These bacteria help in converting the fish waste or ammonia into nitrite and later nitrite gets transformed into nitrate.

Clearly, having live rock in the middle of your tank, and feeding the tank frequently will initiate the nitrogen cycle.

How To Cycle A Tank With Fish Using Traditional Method? 

Firstly, keep an aquarium test kit handy to test the level of pH, ammonia, nitrite, and nitrate all through this process, as it will help you to protect your fishes from an excess amount of toxin exposure. Make sure to select a kit that will give you fast and accurate results.

  • Now adjust the temperature at 74 – 80 degrees F ( 26 – 28 degree C).
  • Add a water conditioner to secure the water for the fishes.
  • Measure the pH and note it down.
  • Buy inexpensive hardy fishes like danios, platys, barbs, gold fishes, molys etc.
  • Add 1 fish to each 2 – 3 gallons of water.
  • Feed them properly. Make sure the filter is running efficiently.
  • Check every alternative week for the amount of ammonia in the tank water.
  • Although zero ammonia is preferred in the tank, to get your ‘aquarium nitrogen cycle’ started you need to wait a bit until the Nitrosomonas bacteria break down ammonia into nitrite.
  • Nitrite will be again broken down by the Nitrobacter bacteria to nitrate. And it will take around 50 – 60 days to complete the cycle.
  • Now just continue checking with the test kit for the level of nitrate. If crossed 10 ppm then change 25 – 30% of the tank water to minimize it.

The only downfall of this method is that your fishes will live in stress because of the excessive level of ammonia and nitrite in the water. Hardy fishes may survive this encounter, but sensitive fishes will not sustain at all. So, once the nitrogen cycle starts to run properly, you can add some additional fishes.

Tips To Keep Your Beneficial Bacteria Colony Growing 

Once, your new tank has its own established nitrogen cycle, you need to maintain the colonies of the beneficial bacteria well, otherwise, the health of your tank will get affected.

Here are some useful tips to keep them growing.

  • Maintaining the place where the bacteria colonies live:

It is for sure, that you will use a filter in your new fish tank, for the proper filtration.

Some of the common filters available on the market are canister filter, under gravel filters, hang-on-the-back filters, and internal filters. Each of these filters has a filter media of large surface, so naturally beneficial bacteria will grow exponentially on them.

But, after a certain period, we all have to change the filter media because of its exhaustion. Doing this will, separate all the beneficial bacteria from the tank which will result in the improper cycling of the tank.

So, the best way to resolve this issue is to have, two filter medias in your tank. As when the time will come to change the filter media, you will replace only one, and other will still have the beneficial bacteria colonies intact.

  • Ensuring Proper Oxygenated Tank Water: 

Beneficial bacteria die due to lack of oxygen. So to keep them alive you need to ensure that the fish tank water is properly oxygenated. Water which comes in contact with air will have enough oxygen. On the other hand, stagnant water has very limited amount of oxygen. So, the more your filter pump will move the tank water, the more oxygen will mix with it. If you don’t already own you should consider buying a good air pump for the aquarium. They are really affordable.

Don’ts To have A Proper Aquarium Nitrogen Cycle: 

  • Do not expose the filter media to air, as the beneficial bacteria will die if it dries out.
  • Do not clean the filter by removing the sponge media.
  • Do not stop the filter pump as it will minimize the level of oxygen in the tank.

Wrap up:

We have covered almost all the possible ways to start a proper nitrogen cycle in your tank. If you have any suggestions or want to add us something more to the article, please let us know in the comment section below.

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