How to Cycle a New Fish Tank in 24 Hours?

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Cycling a new aquarium is the most important step in fishkeeping. Through this lengthy process, you cultivate a more balanced ecosystem in the aquarium.

If you don’t go through this step first, there’s a high chance your fish will suffer from “new tank syndrome.” NTS is the most common cause of sudden fish death in new aquariums.

Fully cycling your aquarium is crucial for the health of your fish. Unfortunately, completing this process takes a very long time, so many people rush things and introduce fish in the tank too early.

However, there are some safe ways to speed up the tank cycle without risking NTS. Keep reading to learn how to cycle your new tank as quickly and safely as possible!

How Long Does It Take to Cycle a Fish Tank?

Cycling a fish tank from scratch takes roughly 6 to 8 weeks. During this long process, your aquarium will go through three different stages.

You need to give the new tank enough time to go through each stage for the cycle to be complete. Introducing fish too early during the process can be very dangerous.

Let’s take a more in-depth look at what happens when you cycle a new tank. This will explain why this long and tedious wait is much worth it.

Here are the three stages of the nitrogen cycle:

– Stage 1: Ammonia

During this stage, bacteria fix nitrogen from rotting matter into the water and soil. If you have a substrate and plants in the aquarium, these bacteria should already be abundant.

You’ll also get a bump in these bacteria during “ghost-feedings” as the food in the tank starts decomposing.

During this stage, the bacteria in the tank will stabilize the available nitrogen in the form of ammonia (NH3). Unsurprisingly, you’ll see a sharp rise in ammonia levels in the water.

Ammonia is hazardous for fish and can cause suffocation, burns, and even instant death. The safest level of ammonia for fish is 0 ppm.

– Stage 2: Nitrites

During this stage, a new set of bacteria begin growing and feeding off the ammonia in the tank. During a ” nitrification ” process, these bacteria convert the ammonia into nitrite (NO2).

Nitrites are less toxic than ammonia but still harmful to fish. The ideal nitrite level for fish is 0 ppm. Values higher than five ppm are toxic and potentially fatal.

The nitrifying bacteria you need to cultivate take a long time to form and multiply. This stage will take a while.

You should test the water ammonia and nitrate concentrations every few days to see how they change. As time goes on, the ratio of nitrites to ammonia will increase.

– Stage 3: Nitrates

Finally, towards the end of the nitrogen cycle, you should see a sharp bump in the nitrate concentrations and an even more significant decrease in ammonia (and nitrites).

During this stage, new bacterial colonies start to form. These bacteria take up the nitrites in the water and oxidize them into nitrate (NO3-).

Nitrate is the least toxic to fish, and most species tolerate values up to 40 ppm without issues (although <20 ppm is ideal).

You’ll know the nitrogen cycle is complete when ammonia and nitrite levels are down to 0 ppm.

This stage also takes a while, so you’ll need to be patient until the new bacteria are fully established.

Why is It Important to Cycle Your Fish Tank?

Fully cycling your fish tank is crucial for the health and safety of your fish. Again, compounds such as ammonia and nitrites are toxic and potentially deadly to aquatic life.

If your tank is not cycled correctly or not cycled at all, these toxic compounds can accumulate rapidly, thereby harming or killing your fish.

Every time you get uneaten foods or waste in the tank (which will often be if you have multiple fish), that’s an opportunity for ammonia levels to rise.

Without beneficial bacteria in the tank, the ammonia doesn’t get neutralized, so it just keeps building up.

Worse yet, ammonia is invisible to the naked eye, so you won’t know there’s a problem until it’s too late.

Remember, the safe tolerable limit for ammonia in is 0 ppm. You don’t want this stuff anywhere near your fish.

Some signs of ammonia poisoning in fish include:

  • Bleeding or tender-looking gills
  • Torn or damaged fins
  • Darkened body color
  • Clamped fins
  • Inflamed streaks across the body
  • Infections
  • Increased mucous production
  • Weakness and lethargy
  • Suffocation
  • Death

In a properly-cycled tank, the ammonia gets detoxified and converted into safe nitrates almost instantly.

Fish can tolerate nitrate concentrations up to 40 ppm, so you get much more leeway to intervene.

Checking the water values daily lets you know when the levels are rising and when it’s time for a water change.

How to Speed Up the Cycling Process?

Waiting for a new tank to cycle is boring. Luckily, you can do a few things to speed up the process.

The best way to shorten the time is by adding the beneficial bacteria directly. You can do so quickly if you already have a cycled tank. If you don’t have a cycled tank to “rob”, consider the following tips.

These will encourage faster bacteria growth:

  • Dechlorinate the water. Chlorine is added to tap water to kill germs. If this chemical makes it into the tank, it will kill the bacteria you’re working so hard to cultivate. Always add a water conditioner if you’re using tap water for your tank. This will neutralize the chlorine and keep the bacteria safe and happy.
  • Use high-quality biological filter media. Bacteria can float freely into the water. But it also helps if you can provide a surface for them to colonize. That’s what biological filter media does. Bio media is cheap and comes as small ceramic rings or tubes. The porous material of bio media offers a vast surface area for the bacteria to populate. This helps you get more bacteria faster!
  • Keep the aquarium filter running. Most of the nitrifying bacteria in the tank will live in your filter. Thus, you need to ensure the filter is getting a constant flow of water. This provides much-needed nutrients and oxygen from the water column that will help the bacteria grow faster.
  • Maintain alkaline water. This surprises many new aquarists. Typically, we associate alkaline pH values with chlorine and disinfectants— things that kill bacteria! But nitrifying bacteria thrive in neutral to alkaline water. You should maintain a water pH of at least 7.0 or slightly higher for best results. A pH under seven will slow down or stop the growth of beneficial bacteria altogether.
  • Bump up the temperature. Most bacteria species grow best in warm environments. Nitrifying bacteria are no different. For the quickest growth, you want to maintain a water temperature between 70-87°F. Temperatures below 65°F will cut down the growth of bacteria by half.
  • Keep the water oxygenated. Aerobic bacteria need oxygen to survive. Nitrifying bacteria fall under this category. You’ll have to provide a constant supply of dissolved oxygen to promote beneficial bacterial growth. The easiest way is by adding an air stone to your aquarium.
  • Reduce light exposure. Nitrifying bacteria grow best in low-light conditions. So, for the duration of the nitrogen cycle, avoid turning on the aquarium lights. Place your tank away from windows or other sources of direct light exposure. If you have plants in the aquarium, keep the light exposure to a maximum of 8-10 hours per day.

These tips help you speed up the nitrogen cycle, whether you’re starting from 0 or already have an established tank.

Next, let’s look at how you can use another cycled tank to speed up the nitrogen cycle in a new aquarium.

How to Cycle a New Fish Tank as Fast as Possible?

The fastest way possible to get nitrifying bacteria in your tank is, well, adding them directly.

Do this, and you get to skip the ammonia stage. You must then wait for the new bacteria to “settle” in the tank.

Meanwhile, you’ll still get small fluctuations in ammonia and nitrites until the bacteria multiply.

So, how do you add pre-existing bacteria? Here are some of the most common ways to do it:

– Use Old Aquarium Water

Already have an established tank? Then, you can just use some water when setting up the new tank and completing water changes.

There are plenty of good bacteria floating freely in the aquarium. When you use water from an old, cycled tank, you’ll introduce some of the good bugs in your new tank. This will kickstart the nitrifying process.

– Use an Established Filter

Up to 70% of all the nitrifying bacteria in your aquarium reside in the filter. That’s the perfect place for bacterial growth thanks to the constant flow of nutrient and oxygen-rich water and the wide surface area of the bio media.

What better way to add a lot of bacteria to a new tank? Just take an old filter and run it in the new aquarium, and you’ll get almost all the bacteria you need in one go.

– Use Seachem Stability

No established aquarium? No problem! You can simply buy the nitrifying bacteria in a bottle. There are tons of such products to choose from.

They’re usually labeled as water conditioners. If you go down this route, I highly recommend Seachem Stability.

Seachem’s “Stability” conditioners come packed full of aerobic, anaerobic, and other facultative bacteria for a well-balanced aquarium ecosystem.

Thanks to new, state-of-the-art technology, the microbes in this product are highly stable and resistant to a wide range of aquarium parameters.

You can use this conditioner to cycle freshwater, marine, cold water, alkaline, and even acidic aquariums!

The best part is that you can use Seachem conditioner for fish-in cycles. The product is harmless to all aquatic life, including fish, plants, and corals.

As long as you maintain the recommended dosage for one week, there are 0 risks of new tank syndrome. There’s also no danger of overdosing, so you can dose the product regularly without fear.


New tanks are a danger zone for aquatic life. You have to cycle a tank first before introducing any fish.

Otherwise, you risk your pets dying from ammonia poisoning. But nobody would blame you for wanting to skip the lengthy and tedious cycling process.

Nitrifying bacteria takes a very long time to colonize a new tank. If you do it all from scratch, you’ll have to wait 6 to 8 weeks.

Luckily, there are a few ways to speed up the cycle and get the good bacteria faster.

The first thing you can do is set up suitable aquarium parameters to encourage bacterial growth.

This includes good filtration, maintaining high temperatures, neutral to alkaline water pH, and keeping light exposure to a minimum.

The second way is by adding the bacteria directly. You can easily do so if you already have an established aquarium.

Use a cycled filter or old aquarium water to kickstart the bacterial colonies. You can also use bottled bacteria if you don’t have an established tank.

A high-quality product like Seachem Stability lets you complete fish-in cycles, cutting the waiting time even further.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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