How to Cycle a Fish Tank: A Complete Guide – 2020


Knowing how to cycle a fish tank is of paramount importance for your fish’s safety and health. While it is certainly possible to start your Tank without cycling the Tank, you do so at the risk of seriously injuring your fish that could lead to their deaths.


Simply put, a ‘cycle’ allows you to set up a natural biological filtration system that neutralizes the toxic buildup of bacteria in your Tank. It is allowing small bacterial colonies to grow in the Tank.


Could compare the analogy to the gut microbiome in human stomachs. The tiny microorganisms can prevent diseases and fight off toxicity in the stomach. It is what cycling is all about.


In the context of a fish tank, we call this the “Nitrogen Cycle.” Other common names for this phenomenon include the biological cycle, 

The “New Tank Syndrome” and the Nitrification Process. They all refer to the same thing.


Why is the Nitrogen Cycle so Important?


For starters, your fish will generate a lot of waste during a single day – this ‘poo,’ also referred to as the ‘bioload’ – is broken down into ammonia. And ammonia is deadly. It’s the kind of poison that can quickly and mercilessly kill your entire stock. 


No human would ever want to be surrounded by their pee and poo to put things in perspective. And fish are just a whole lot more sensitive. In the wild, this isn’t a problem because an infinitely large body of water surrounds them. A few ammonia deposits don’t do much to alter the quality of the water.


It is where beneficial bacteria come in to play. They filter your water and neutralize the fish’s waste. One of the most significant indications of your Tank overrun by nitrogen is the proliferation of algae, unusual behavioral symptoms in your fish, and near loss of appetite. It is why a tank cycle is necessary.


How Long Does it Take for Good Bacteria to Grow in a Fish Tank?


The growth of ‘good’ bacterial colonies in your Tank will take anywhere from 4 to 6 weeks. The amount of bacteria that grow is directly dependent on the number of waste products available in the Tank.



nitrogen cycle






Understanding the Nitrogen Cycle





During this process, the Tank’s ammonia levels will sharply rise and then slowly drop as the bacteria break it down into nitrite. The Tank will become a little cloudy when this starts to happen. When the levels of ammonia start declining, your Tank is ready for stage 2.




As the levels of ammonia decrease, you’ll see a spike in the ranks of nitrites. It is also very toxic to your fish. You’ll have to continue building the bacterial colonies up until the levels of nitrite again start shrinking.


It will happen at the end of the first week or the start of the second week of your cycle. The nitrifying bacteria will then break up the nitrites into nitrates.




Once your nitrites reach critical mass, your Tank will develop Nitrobacter, a type of bacteria. These bacteria will convert the nitrites into nitrates. Once your ammonia and nitrites levels reach 0ppm (parts per million), you have successfully cycled your Tank.


A word on nitrates: Nitrates are the final chemical product in the nitrogen cycle. They are not harmful to your fish – in small quantities. But if you allow the nitrate levels to rise too much,


they will become toxic to your fish. Nitrate levels above 20ppm can be harmful to your species, and they will start getting poisoned. Make sure to monitor the stories in your Tank.


The good news is that you can quickly lower the nitrate level down to harmless levels by performing a simple water change. It is one of the main reasons why we recommend changing the water regularly.


Alternatively, you can also add aquarium plants that can use the nitrates. They are instrumental in a saltwater tank. The live rock has anaerobic pockets where denitrifying bacteria actively break down the nitrates into nitrogen gas, which is harmless.


How to Grow Good Bacteria in Fish Tank?


Start by slowly introducing ammonia supplements in your Tank, to the tune of 1 to 2ppm (parts per million). Run the filter and allow the bacteria to break down the ammonia. Add more ammonia to the Tank for about one week (1 to 2ppm of ammonia).


It won’t be long before the oxygen-loving colonies set up shop near the aquarium filter, where there is plenty of oxygen to survive.


This entire process can take a few weeks and even two months, depending on the Tank size (and how well you’re doing).



How Can I Tell if the Tank has Started its Water Cycle?



Once the ammonia quantity reaches 0 ppm, your Tank has cycled itself.


You will use a water kit to test for the presence of ammonia.


There are many ways to cycle fish aquariums, some ethical (such as fishless cycling), and some not so honest (using existing fish stock to cycle the Tanka poisonous process that will end with their death).


We merciful to your little companions and use the fishless cycle. With a little bit of patience and time, you will create a healthy tank cycle.


What Happens if You Don’t Cycle a Tank?


If you add your fish to an uncycled aquarium, things will look pretty smooth at first. But as the bioload starts to build up (aka poop) and the uneaten fish food gets broken down – your Tank’s ammonia levels will begin to rise, and rise, and grow with nothing to stop it.


Some people call this the ‘fish cycling’ process. But it will prove deadly to your fish.


The toxic environment is very hard on your fish, and most will not survive the cycle. The ones who do make it at the end of the day will have a compromised immune system and won’t live very long.


We don’t recommend buying fish before cycling your Tank – because if you do, a fish-in cycle may be the only way to establish a nitrogen cycle.


How to Cycle a Fish Tank


When it comes to cycling your fish Tank, you need just about three products.

An Aquarium Test Kit to Keep Track of the Quality Levels 

It is important because the nitrogen process is entirely invisible to the naked eye. The best way to truly understand what’s going on inside your Tank is to test it for the presence of ammonia using a water testing kit.


We recommend buying an all-in-one mater test kit because it contains every test you need to cycle your Tank at one low cost.


Here is an in-depth YouTube tutorial on using a freshwater master test kit (may also work for a saltwater tank).


  • Ammonia Supplements


Instead of waiting for the Tank’s bioload to breakdown into ammonia, you can speed up the process by adding ammonia directly. It allows you to keep ammonia levels constant.


It is essential to use 100% pure ammonia for this process. Standard household ammonia salts are not pure enough and come loaded with scents and additives. It will kill your tank cycle before it even starts.


Just use pure ammonia, like the one here on Amazon.


  • Add a Dechlorinator


Most fishkeepers try to use regular tap water (it is cheaper and saves the time spent going to a pet store). But your tap water may contain chlorine and chloramine, two deadly chemicals that can neutralize your bacteria (and prove harmful to your fish).


However, you can use a dechlorinator to make your water safer for the fish and the beneficial bacteria.


Use a dechlorinator whenever you plan on adding tap water to your aquarium.


With these three products on hand, it’s time to start cycling your aquarium in X simple steps.


Note: Read and understand each step carefully before moving to the next step. Failure to follow each step may ruin the cycle. If this happens, you may have to start over.


Step 1: Set up the Aquarium


To learn how to set up an aquarium, check out our guide here.


The guide covers all the things you need, including an air pump, substrate, plants, heater, and filter.


It is essential to fully set up the Tank because bacteria need a surface to live. Ideal spots for bacteria to live on is the filter media and the substrate. Most bacteria will live on the filter media.


Ensure all the electrical equipment such as bubblers, heaters, and filters running during the cycling process. It creates the ideal circumstances for the beneficial bacteria to grow and may speed up the process.


Keep the temperature between 66 to 80 degrees Fahrenheit. Growth outside of this temperature can take longer to complete. Use an aquarium thermometer to check your water temperature accurately.


To summarize: set up the Tank completely and switch on all the devices.


Step 2: Check the pH Value


It is an important step that most aquarists often miss, thus, resulting in a failed cycle.


If the Tank’s pH level drops below neutral (7), the cycling process will either slow down or completely stop.


Most master test kits include pH tests. Make sure to put them to fair use.


If the water’s pH value is below 7, you will have to raise it back up before you can move on to the next step.


In most cases, this isn’t difficult to achieve because most homes have water at a pH value higher than 7.


You should regularly monitor the Tank for pH levels. If it drops under 7, a simple 30% partial water change can restore the PH value and kickstart the cycle again.


To summarize step 2: Regularly check the water’s pH value and adjust when it goes below 7.


Step 3: Adding Ammonia to the Tank


In a new tank, there will not be any ammonia amount. It means that the bacteria will have nothing to break down—That’s why you should add the ammonia yourself.


Take your ammonia supplements and follow the instructions.


To add the correct ammonia of water, you need to know how much water is present in the Tank. Start measuring your ammonia.


As a general rule, fish tanks smaller than 40 gallons should add 2ppm of ammonia. If the water level is higher than 40 gallons, add 4ppm ammonia.


Although it is possible to use the measuring spoons in your kitchen, it is preferable to buy a set of measuring tools instead.


Allow the ammonia to distribute evenly throughout the water. Next, measure the ammonia levels using your ammonia test. Try not to ignore any of the instructions if you want to achieve accuracy.


If your ammonia readings are less, then add more ammonia.


If your ammonia readings are higher, perform a water change. It will bring the ammonia level down.


Note: Do not add more than 5ppm ammonia because it will slow down the cycling process. Be patient!


The next step is a waiting game and will take about a week to initiate. Check your ammonia levels every day with the test kit. You’re waiting for the ammonia levels to plummet. Once this takes place, you can move to the next step.


Summarizing step 3: Add ammonia, test the ammonia levels every day, ensure the pH value stays at 7.


Step 4: Time to Test for Nitrites


At this stage, your ammonia eating bacteria will start to form. Use your nitrite test kit and measure their levels.


If you see a positive test, your cycle has started.


It is essential to make sure that the bacteria have enough ammonia to eat. Do not allow the ammonia levels to reach zero because the bacteria will start to die, and you’ll have to start the whole thing all over.


To give your bacteria more ‘food,’ add only half of the ammonia that you added in step 3. Make sure the ammonia level never exceeds 5ppm.


Now, wait for the nitrite levels, testing every day. Once your nitrite levels start dropping, it’s time to move to the next step.


Summarizing Step 4:

  1. Once you detect nitrites, add more ammonia.
  2. Test for ammonia and nitrite levels.
  3. Do not allow the pH to go below 7.


Step 5: Check for Nitrate Levels


In about a week, your nitrite eating bacteria will start to form. You can check for their presence by testing for nitrates. If the test comes out to be positive, your Tank is in the final stage of the cycling process.


Make sure your bacteria have enough ammonia to eat. Add half a dose of ammonia (or as needed) every day to keep the levels above 1ppm.


Continue to test the water.


The moment your bacteria can consume a half dose of ammonia (including resulting nitrates) in 24 hours, you have established the nitrogen cycle.


You are summarizing—Step 5: Test for the growth of nitrates. Add half doses of ammonia. When both ammonia and nitrates read zero after 24 hrs, your cycle is complete.


Step 6: The Efficiency of Your Bacteria


The final step is to check for the efficiency of your bacteria.


Please wait for the ammonia and nitrite levels to completely deplete and add a dose of ammonia until it’s at about 4ppm or the same amount added in step 3.


Test the ammonia and nitrite levels after 24 hours have passed. If both read zero, you’ve succeeded.


Your Tank is now fully cycled.


It can take about a month to cycle an aquarium.


Wrapping Up



So there you have it, the complete step by step guide to cycling an aquarium. You have now provided your fish with the best possible chance of living a productive and happy life.


Just remember one thing: you’re not in the clear yet. The nitrogen cycle will run in the background and function like clockwork, but many factors could disrupt it.


Perhaps your fish is producing too much bioload for the bacteria to handle in a day. Or maybe the uneaten food is contributing too much to the bioload. Worse still, perhaps the filter has stopped working and needs changing.


You have to keep an eye out for these little things. Make sure to continuously monitor your ammonia and nitrite levels to ensure your Tank is operating as it should.

Related Articles

How to Think and Act in the Plummeting Stock Market

People live better in big houses and in big clothes. I try to contrast; life today is full of contrast. We have to change!...

The Real Economy Has Never Been Tested by a Pandemic

People live better in big houses and in big clothes. I try to contrast; life today is full of contrast. We have to change!...

More and More People Stay Home as Coronavirus Spreads

People live better in big houses and in big clothes. I try to contrast; life today is full of contrast. We have to change!...

Stay Connected

- Advertisement -

Latest Articles

How to Think and Act in the Plummeting Stock Market

People live better in big houses and in big clothes. I try to contrast; life today is full of contrast. We have to change!...

The Real Economy Has Never Been Tested by a Pandemic

People live better in big houses and in big clothes. I try to contrast; life today is full of contrast. We have to change!...

More and More People Stay Home as Coronavirus Spreads

People live better in big houses and in big clothes. I try to contrast; life today is full of contrast. We have to change!...

Witnessing the Birth of the New Coronavirus Economy

People live better in big houses and in big clothes. I try to contrast; life today is full of contrast. We have to change!...

Companies Are Putting Profits Ahead of Public Health

People live better in big houses and in big clothes. I try to contrast; life today is full of contrast. We have to change!...