Three Ways to Cycle Your New Aquarium: Part 2 of the Nitrogen Cycle Series
Three Ways to Cycle Your New Aquarium: Part 2 of the Nitrogen Cycle Series
Mayur Dev|
Aquarium Cycling Series – Part 2: Fishless, Fish-In, and Seeded Cycling Explained
In the first part of this series, we explored why every aquarium needs a functioning nitrogen cycle before fish are introduced. We looked at how beneficial bacteria process toxic waste and why New Tank Syndrome remains one of the biggest causes of fish loss in newly established aquariums.
Now it's time to answer the practical question every beginner asks:
How do you actually cycle a new aquarium?
There are three recognised methods for establishing a biological filter, and each suits a different situation. The right choice depends on whether you're setting up a brand-new aquarium, you've already added fish, or you have access to an established tank that can provide mature filter media.
In this guide, we'll explain all three approaches, their advantages, and the situations where each method works best.
Before You Begin: Three Essential Requirements
Regardless of which cycling method you choose, a few basic conditions must be in place from the very beginning.
Keep the Filter Running at All Times
Beneficial bacteria don't live suspended in the water. They attach themselves to filter media and other solid surfaces, forming stable bacterial colonies.
Because these bacteria require a constant supply of oxygen-rich water, the filter should remain switched on 24 hours a day throughout the cycling process. Turning it off for extended periods can deprive the developing colony of oxygen and significantly slow—or even reverse—its progress.
Always Remove Chlorine Before Cycling
Tap water commonly contains chlorine or chloramine to make it safe for human consumption, but these disinfectants are harmful to both fish and beneficial bacteria.
Every drop of water added to the aquarium—whether during the initial setup or later water changes—should be treated with a reliable conditioner first.
Sunken Garden Anti-Chlorine instantly neutralises chlorine and chloramine, binds heavy metals, and also introduces 15 strains of beneficial bacteria, giving your developing biological filter additional support throughout the cycling process.
Maintain a Stable Temperature
Beneficial bacteria reproduce most efficiently in warm, stable water.
A temperature between 26°C and 28°C provides ideal conditions for bacterial growth. Cooler temperatures slow colony development, while excessive heat can reduce bacterial activity.
Keeping the heater set around 26–27°C throughout cycling helps establish the nitrogen cycle as efficiently as possible.
Method 1: Fishless Cycling (Recommended)
Estimated Time: 3–5 weeks
With Sunken Garden Good Bacteria: Approximately 2–3 weeks
Risk to Fish: None
Difficulty: Beginner Friendly
Fishless cycling is widely regarded as the safest and most reliable way to establish a new aquarium.
Instead of exposing fish to toxic ammonia while beneficial bacteria develop, you create the bacterial colony first and only introduce livestock once the aquarium is biologically stable.
Because no fish are present during the process, there's no risk of ammonia or nitrite poisoning, making this the preferred approach for beginners and experienced aquarists alike.
Step 1: Set Up the Aquarium
Begin by completely assembling the aquarium exactly as it will operate once stocked.
Add substrate, hardscape, decorations, and equipment before filling the aquarium with tap water treated using Sunken Garden Anti-Chlorine.
Install the filter, switch it on, and set the heater to approximately 26–27°C.
Running the complete system from the beginning provides the warm, oxygen-rich environment beneficial bacteria need to colonise the filter media.
Step 2: Provide an Ammonia Source
Beneficial bacteria cannot establish without food.
Since their primary energy source is ammonia, you'll need to introduce one artificially before adding fish.
Several methods work well:
- Raw prawn: Place a small piece inside a mesh bag and allow it to decompose naturally. As it breaks down, it releases ammonia into the water. Replace it once fully decomposed.
- Pure ammonia solution: Dose carefully to achieve approximately 2–4 ppm ammonia, confirming levels with a water test kit. This offers the greatest control but requires pure, additive-free ammonia.
- Fish food: Adding a small pinch each day allows the food to decompose gradually and release ammonia. Although slower than the other methods, it remains a practical option for many beginners.
Step 3: Add Beneficial Bacteria
To speed up colony development, dose Sunken Garden Good Bacteria from the first day of setup.
Add 1 ml per 10 litres directly into the filter intake while the filter is operating.
Rather than waiting for bacteria to establish naturally, this immediately introduces live bacterial strains into both the filter media and aquarium surfaces.
Continue dosing daily throughout the first week to encourage rapid colony development.
We'll explore the science behind Good Bacteria in greater detail in Part 3 of this series.
Step 4: Monitor Water Parameters
Cycling should always be guided by water testing rather than guesswork.
Using TCWS Water Test Strips, check ammonia, nitrite, and nitrate every two to three days.
As the cycle progresses, you'll notice a predictable pattern:
- Ammonia rises before gradually falling.
- Nitrite appears as ammonia decreases.
- Nitrite eventually falls while nitrate becomes detectable.
These changing values show the bacterial colonies developing and taking over waste processing.
Step 5: Confirm the Cycle
Before adding fish, it's important to verify that the bacterial colony can process waste quickly enough.
Add one final dose of your chosen ammonia source and test the water 24 hours later.
If ammonia has returned to 0 ppm within that period, the biological filter is capable of handling livestock safely.
If measurable ammonia remains after 24 hours, continue cycling for several more days before testing again.
Step 6: Introduce Fish Gradually
Once the aquarium is fully cycled, perform a 50% water change to reduce accumulated nitrate.
Rather than stocking the aquarium all at once, introduce fish in stages.
Adding roughly one-third of your planned livestock every couple of weeks allows the bacterial colony to expand naturally as the aquarium's waste production increases, helping maintain long-term biological stability.
Method 2: Fish-In Cycling
Estimated Time: 4–6 weeks
With Sunken Garden Good Bacteria: Approximately 3–4 weeks
Risk to Fish: Moderate (requires active management)
Difficulty: Intermediate
Sometimes fish are already living in a new aquarium before the owner learns about cycling.
Whether through an impulse purchase, advice from a retailer, or simply not knowing about the nitrogen cycle, this situation is common among beginners.
Although fish-in cycling isn't the preferred approach, it can be managed successfully with careful monitoring and consistent maintenance.
The primary objective is to keep ammonia and nitrite below harmful levels while the biological filter gradually establishes itself.
Dose Beneficial Bacteria Immediately
Begin dosing Sunken Garden Good Bacteria as soon as possible.
Use 1 ml per 10 litres every day from the first day onward.
Introducing beneficial bacteria early shortens the period during which fish are exposed to toxic waste, allowing the nitrogen cycle to develop more quickly.
Continue Fish-In Cycling with Daily Monitoring
During a fish-in cycle, consistency is essential.
Test the water every day and monitor both ammonia and nitrite closely. If ammonia rises above 0.5 ppm or nitrite exceeds 0.25 ppm, perform an immediate 25–30% water change using temperature-matched, dechlorinated water.
Continue treating every water change with Sunken Garden Anti-Chlorine, which protects the developing bacterial colony while neutralising chlorine and chloramine.
Feed sparingly throughout the cycling period. Smaller meals produce less waste, reducing the amount of ammonia entering the aquarium. Offer only what your fish can finish within two minutes and remove any uneaten food.
Avoid cleaning the filter during this time. The beneficial bacteria establishing your biological filter live primarily on the filter media, and cleaning it too early can significantly slow the cycling process.
Most importantly, resist adding more fish until testing confirms 0 ppm ammonia and 0 ppm nitrite.
Method 3: Seeded Cycling
Estimated Time: 7–14 days
With Sunken Garden Good Bacteria: Often even faster
Risk to Fish: Low with proper monitoring
Difficulty: Intermediate
If you have access to an established aquarium, seeded cycling is the quickest way to prepare a new tank.
Instead of waiting for bacteria to develop naturally, you transfer mature filter media from a healthy aquarium into the new filter. This instantly introduces an active bacterial colony, dramatically reducing the cycling period.
Suitable sources include:
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Filter media from your own established aquarium.
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Media from a trusted hobbyist's tank.
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Used filter sponge from a reputable aquarium store with healthy livestock.
The more mature media transferred, the faster the new aquarium will stabilise.
To strengthen the colony further, dose Sunken Garden Good Bacteria during setup. The transferred media provides an immediate foundation, while the bacterial supplement helps expand and diversify the biological filter.
Although seeded tanks cycle much faster, regular testing is still essential. Introduce fish gradually and continue monitoring ammonia and nitrite until the aquarium consistently shows 0 ppm for both.
Which Cycling Method Should You Choose?
The right method depends on your situation.
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Setting up a brand-new aquarium? Fishless cycling remains the safest and most reliable approach.
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Already have fish in the tank? Fish-in cycling can be successful with careful testing, regular water changes, and daily bacterial supplementation.
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Have access to mature filter media? Seeded cycling offers the fastest route to a biologically stable aquarium.
Regardless of the method you choose, patience is key. Allowing the nitrogen cycle to develop properly creates a healthier aquarium, reduces stress on your fish, and provides a strong biological foundation for long-term success.
In Part 3, we'll take a closer look at beneficial bacteria—how they work, why they speed up cycling, and how to use Sunken Garden Good Bacteria effectively to establish a healthy aquarium faster.
👉 Continue to Part 3: How Sunken Garden Good Bacteria Accelerates the Cycle →
👉 Shop Sunken Garden Anti-Chlorine | Shop TCWS Water Test Strips
Questions about which cycling method suits your situation? Write to us at info@mayurdevaquascaper.com