Why Nitrite Level is Not Dropping and How to Speed up the Process

Every new tank has to go through the process of cycling. Cycling refers to establishing a colony of bacteria that will remove toxic waste in the aquarium.

In this process ammonia turns into nitrite and nitrite turns into nitrate. But many times, the cycle gets stuck into nitrite, and nitrate levels do not drop. What is the reason for cycling tank nitrite not dropping?

The reasons can be many. Adding too much ammonia or excess food, and not enough water change is the common reason for nitrite not dropping.

But you can speed up the process by applying some methods which I will talk about later in this article.

What is Nitrite?

Nitrite is a toxic element that by produced by the breakdown of the waste of the fish. Bacteria in the fish tank help to break down the waste.

In a fishless tank cycling, you have to add ammonia so that those ammonia-eating bacteria can grow and break it into nitrite.

Afterwards, nitrite-eating bacteria will eat the nitrite and produce nitrate, which is slightly less harmful to the fish.

Reasons Why Nitrite Level is Not Dropping in the Cycle?

Nitrite levels not dropping while tank cycling is a very common problem among aquarists. If you are facing the same problem know that you are not alone.

There are some reasons why your nitrite level may not drop.

1. Bacterial Growth

Bacteria which convert ammonia to nitrite and the bacteria which convert nitrite to nitrate are different. Both take different times to grow in the aquarium.

Ammonia-eating bacteria grow faster than nitrite-eating bacteria. For this reason, you will see ammonia level 0 very quickly and nitrite level is not decreasing.

That is because nitrite-eating bacteria are not grown yet in the tank.

2. Adding Too Much Food or Ammonia

As it takes a long time to grow nitrite-eating bacteria to grow, people make mistakes and think they need to add more ammonia to continue the cycle.

But what it does is, increase the nitrite level. It becomes so high that it takes a long time to lower the level.

Another thing is, giving excess food. It does the same thing. Many people think that bacteria will starve if they do not give food daily. It is just a misconception. Bacteria do not need food every day as we do.

3. Not Changing Water

You need to change the water when the nitrite level is high. If you keep the water that way nitrite will not drop in any short time.

Changing 30-50% water dilutes the nitrite fill water with nitrite-free water. It helps to reduce the level pretty quickly.

4. Low pH Level

If your cycling process is stuck at some point there is a chance that the pH level of the water is low.

The pH level should be between 7 to 8 in a tank cycling. It helps the bacteria to grow in a fair amount of time.

On the other hand, low pH delays the process.

5. Unsuitable Temperature

The bacteria will grow in your tank comfortably if the temperature in it is suitable for them. The best-suited temperature of the cycling tank is 70 to 80 °F (21 to 27 °C).

Higher or lower than this heat can cause damage in the cycling process. Nitrite or any certain element will not reduce accordingly if the temperature is not right.

How to Speed Up the Process?

The truth about cycling a tank is that it is not an instant process. You have to be patient while doing it. because it will take time.

But as I mention some of the reasons why nitrite dropping may delay the whole system, there are some ways also, which can decrease the time. Here are some of them.

1. Get the Fundamentals Right

You need to get the basic things right to get the cycling going in the right direction.

Nitrite not dropping in a cycle is one of the causes that fundamental things are not right. It makes the entire thing stuck in the middle.

Things you should be checking:

pH Leve Above 7

The bacteria you are trying to grow to need a pH level between 7 to 8. At this pH level, the growth will be steady.

But if it goes below 7 the cycling will be much slower or worse it will stop.

Your master test kit has a pH test kit as well. Check it.


The same goes for the temperature of the tank water. Keep the heat at 70 to 80 °F (21 to 27 °C).

If it goes below 70°F the cycling will go slow. If it goes below 65°F the cycling will stop in the middle.


Just like all the other living organs, bacteria also need oxygen to live. To get enough oxygen going in the tank keep the filter on.

Most of the bacteria live in the filtration system of your tank. If you turn off the filter, the bacteria deprive of oxygen and stop growing.

Use Water Conditioner 

Tap water contains chlorine and chloramines which is harmful to the beneficial bacteria. If you directly add tap water into your tank, it can kill all the bacteria.

Always use a water conditioner before you add tap water into the tank.

2. Get Stuff from a Used Aquarium

A running aquarium that has gone through a cycle already can be your gem. It is overflowing with bacteria with are trying to grow.

If you take some bacteria from that and put it into your tank it will considerably fasten the process.

There are several ways you can do it:

Take the Used Filter

Take the filter from that tank and insert it into your cyclable tank. most of the good bacteria live inside the tank. With the water flow, your aquarium will fill with bacteria in no time. 

Cultivate in Your Filter

You can insert your filter in an old tank beside the existing filter. As there is already a lot of beneficial bacteria in it, the filter will also fill with it in just one week.

After that, your can take your filter and set it in your tank and see the magic.

In the same way, you can use gravel from that old tank. one cup of gravel will go the job.

Add Plants

Plants are a great way to add surface to your tank. Beneficial bacteria can grow on that surface so easily.

Buying some plant from an old tank is another way you can fasten your cycling.

3. Bottled Bacteria

Nowadays many brands are coming up with living bacteria in a bottle. The process and bottled-up bacteria so you can put it in your tank.

It will help to establish bacteria in the cycling tank faster.


While cycling a tank, the most important thing you are going to need is patience. Because this is going to take a long time, even months. And if you make any mistakes, it will take even more. Making mistakes are natural.

n and go for it. Hope this article has taught you some good you can apply to your project.

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Arif H Fahim

Welcome to PetFishTank! My name is Arif. I make an effort to publish educational articles using my many years of expertise as a fish owner.

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