How Long Does It Take For Ammonia To Turn Into Nitrite?

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Many aquarists know that aquariums require nitrifying bacteria that turn ammonia into nitrites. But not everyone knows how long it takes. As I asked this question myself pretty frequently in the past, I decided to dedicate an entire article to it.

It takes 7 to 10 days for ammonia to turn into nitrite. After another 14 to 21 days, nitrties will start turning into nitrates. The entire process, known as the nitrogen cycle, takes between 6 and 7 weeks.

As we move forward, I will elaborate on what can speed up this process or, on the other hand, stop it from happening. Then, I’ll show you some tricks that will allow you to add fish immediately without waiting so long.

Still curious? Feel free to check my complete guide on aquarium ammonia, where I discussed what causes ammonia, how to get rid of it, what equipment to use, and much more.

How Long Does It Take For Ammonia To Turn Into Nitrite?

The term ‘Nitrification’ refers to a process where bacteria turn ammonia into nitrite. Eventually, that nitrite becomes nitrate which plants can consume.[1]

Nitrification is just as common in aquariums as it is in the wild. However, where aquariums are concerned, you must deliberately initiate the nitrification process by introducing ammonia to the tank.

Usually, you don’t want ammonia in the aquarium. But in this case, you want the substance to accumulate. 

Aquarists achieve this objective by adding food, dead fish, and other organisms that generate ammonia when they decompose.

The ammonia concentration will continue to increase until nitrifying bacteria called Nitrosomonas appear.[2] They will turn the ammonia into nitrite. 

You may see this happen within ten days.[3] The ammonia levels will gradually drop while the nitrate concentration rises, proving that you have a healthy population of nitrifying bacteria. 

However, this timeline is not fixed. It can take some tanks as many as two weeks to register significant nitrite levels.[4] The wrong conditions can extend this duration.

How Can I Speed Up The Nitrite Cycle?

The nitrogen cycle can take weeks to complete. Some people create delays by introducing the wrong conditions. Others interrupt the process altogether, ruining all their hard work.

Fortunately, there are ways to do the opposite. You can use the following steps to speed up the nitrite cycle:

1. Get Premade Commercial Bacteria

You can buy bottles of nitrifying bacteria from fish stores. Rather than waiting for the bacteria to form naturally in the water, you can add spores of premade nitrifying bacteria.

Given time, they will grow. This makes the nitrite cycle less of a gamble. You don’t have to wonder whether or not nitrifying bacteria will form.

If you like this option, I personally suggest getting the API QUICK START Nitrifying Aquarium Bacteria (link to Amazon). It is extremely easy to use and will prepare your tank in no time.

2. Adjust The Ammonia Levels

Most people don’t associate water changes with the nitrogen cycle. However, you have to realize that high ammonia concentrations are dangerous to nitrifying bacteria.

With most ammonia solutions, you must restrict the dose to 4 drops per gallon. As a rule of thumb, keeping ammonia at 2-3 ppm is best.

Excess ammonia will inhibit the functions of the nitrifying bacteria.[5] Therefore, if you think you have added too much ammonia, perform a water change to reduce the concentration.

3. Remove Tap Water Chlorine

Use water conditioners to purify new water, especially if it comes from a tap. Tap water has chlorine, and chlorine will destroy the nitrifying bacteria.

If you don’t understand why your population of nitrifying bacteria is so small, test the water. If you’ve detected chlorine, use a de-chlorinator.

I personally use the SJ WAVE 6 in 1 Aquarium Test Strip (link to Amazon) to monitor chlorine levels. There should be zero chlorine in fish tanks.

You can quickly eliminate it with products like the well-known Seachem Prime Conditioner (link to Amazon). Use two drops per gallon.

Another thing I typically recommend is letting the water sit 24 hours before adding it to your tank. That will allow toxic elements like chlorine to evaporate and stabilize the water’s pH by reducing carbon dioxide.

4. Place An Old Filter

The nitrite cycle takes a long time because you’re trying to nurture a colony of nitrifying bacteria from scratch. But what if you introduced filter media from established tanks? You find an aquarium’s beneficial bacteria in the filter media.

Placing that filter media in a young tank allows the established colony of nitrifying bacteria to expedite the nitrification process in the young tank.[6]

You can either use the filter media or the entire filter. If you have never done this before, I suggest placing the entire apparatus as is.

5. Adjust The Water Conditions

As a rule of thumb, I suggest keeping the temperature at 83 to 87 degrees F. Extreme temperatures prevent the bacteria from growing.

Keep the pH at 7 to be on the safe side. A lower pH will slow the growth of the bacteria. Although, the pH is not quite as critical as the oxygen.

Like all living organisms, bacteria need oxygen to thrive. This is why air pumps and stones are essential to cycling aquariums.

6. Bring Gravel From Another Tank

Take gravel from an established tank and add it to the new tank. Nitrifying bacteria typically grow on the substrate in established tanks. Therefore, taking that gravel to the new tank will bring the nitrifying bacteria along.

  • For your convenience, here is an excellent Youtube video that shows how to cycle a fish tank fast:

Why Is The Ammonia Not Converting To Nitrite?

A successful nitrogen cycle is not a guarantee. Sometimes, factors like those below can prevent the conversion of ammonia to nitrite.

If you see that the process isn’t moving, here is a checklist of things you should consider:

  • Parameters

What are the parameters? Is the temperature too high or too low? Extreme temperatures will affect the bacteria’s reproduction rate.

Check the heater. Has it malfunctioned? What about the pH? What do the testing strips say? Don’t expose nitrifying bacteria to a low pH.

  • Toxins

Chlorine will prevent the nitrification process by killing all the nitrifying bacteria. This also applies to chloramine. In fact, chloramine is worse because it is more stable than chlorine.

  • Ammonia

How much ammonia did you add to the aquarium? Some people add too much ammonia. They are unaware of the harm they are doing.

Others don’t add enough ammonia. They don’t realize that bacteria feed on ammonia, and insufficient ammonia levels can reduce the bacteria’s reproductive rate.

You have to find a balance. Stick to 4 drops per gallon. Don’t be afraid to perform water changes if you add too much ammonia.

  • Oxygen

Bacteria cannot survive without oxygen. They need oxygen to thrive. They also need oxygen to turn ammonia into nitrite. Therefore, the nitrification process is unlikely to occur if you have an oxygen deficiency.

What Are The Signs Of A Cycled Fish Tank?

You initiate the nitrogen cycle by adding ammonia to the water. The ammonia concentration will initially increase. But after a few days or weeks, ammonia levels will fall while the nitrites increase.

But the cycling process is not done. You also want the bacteria to turn the nitrites into nitrates. Therefore, as the nitrates increase, the ammonia and nitrites will decrease.

You can’t say that the tank is cycled to completion until the ammonia and nitrite levels reach zero. The nitrates should sit at 20ppm or less.

You can test your theory by adding fish to the tank. If you adjusted the parameters to aid the cycling process, switch them back to the range the fish demand.

Fish in a cycled tank will exist peacefully and show no signs of stress. You will also find that the tank is easier to maintain. One water change per week is more than adequate.

You cannot keep the ammonia concentration down in an uncycled tank, which is why you should keep a testing kit on hand. Don’t just assume that the tank is cycled simply because you have been waiting for six or more weeks.

To measure the pH, nitrates, nitrites, and ammonia, I got the API FRESHWATER MASTER TEST KIT (link to Amazon). This one is a bit more expensive than average, but it lasts for eight hundred measures, which is pretty impressive.

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When done naturally, it will take seven to ten days for ammonia to turn into nitrties. For this to happen, you need a functioning filter, an air stone, and a heater. This will create a conducive environment for nitrifying bacteria formation.

If you wish to speed up this process, you can get premade bacteria, such as in the API QUICK START mentioned earlier. This will allow you to add fish to a new tank immediately.

You can also introduce a used filter or gravel from a cycled tank. These usually contain the proper amount of nitrifying bacteria. Either way, keep the temperature between 83 and 87 degrees F and the pH at 7.