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How to Cycle a New Aquarium Without Stressing Your Fish

When embarking on the exciting journey of setting up a new aquarium, one crucial aspect you must acquaint yourself with is the nitrogen cycle. 

Cycling your aquarium is a vital step that involves establishing a healthy beneficial bacteria colony within your tank.

This colony plays a pivotal role in breaking down the waste products produced by your fish and plants, creating a stable and safe environment for your aquatic life to thrive.

In this comprehensive guide, we'll delve into the primary methods of cycling a new aquarium and equip you with the knowledge and tools to accomplish this essential task with success and care.


Fishless Cycling. If you somehow have the patience to put off adding fish for a few weeks, there are a few ways to give it a great start. You can use live plants or "used" filter media from another tank to introduce helpful bacteria. Another option is adding a special bacteria boosting product like Seachem Stability.

For about two to six weeks, let your tank cycle without fish but do regular water changes. Remember to test your water to monitor the levels of ammonia, nitrates, and nitrites. After this, you can introduce sturdy fish like endlers, guppies, or danios to help your beneficial bacteria colonies grow. They'll make sure everything's ready for your future aquatic pals!


Fish-In Cycling. If you opt for fish-in cycling, carefully introduce a few hardy fish, such as zebra danios, white cloud minnows, or cherry barbs. Remember, these fish will play a crucial role in kickstarting the cycling process, so select them wisely.

Plant Cycling. Our favorite method transforms your tank into a thriving ecosystem. Start by adding live plants—better at dealing with waste than bacteria alone, according to microbiologist Diana Walstad.

Once your plants or algae show new growth, the cycle's done. Introduce a few fish, feed moderately, and test water until ammonia and nitrites are 0 ppm, nitrates under 40 ppm. It's all about creating a lush, balanced habitat!

Step-by-Step Guide to Properly Cycle Your New Aquarium:

  1. Setting Up Your Aquarium: Before commencing the cycling process, ensure you have properly set up your aquarium with the necessary equipment, substrate, decorations, and dechlorinated water. Activate the filter and heater, and adjust the temperature to suit the specific needs of the fish species you intend to house.
  2. Daily Water Testing and Maintenance: Regardless of the method you choose, daily water testing for ammonia, nitrite, and nitrate levels is imperative. For fishless cycling, add more ammonia whenever the level drops below 1 ppm. For fish-in cycling, perform partial water changes whenever the ammonia or nitrite level exceeds 0.25 ppm.
  3. Establishing the Beneficial Bacterial Colony: Be patient as you wait for the ammonia and nitrite levels to drop to zero and the nitrate level to rise. This indicates that the beneficial bacterial colony has successfully established itself and can handle the bioload of your aquarium (as long as you increase the number of inhabitants slowly).
  4. Completing the Cycling Process: For fishless cycling, perform a substantial water change to lower the nitrate level below 20 ppm. For fish-in cycling, gradually add more fish over time until you reach your desired stocking level. Ensure you're not overstocking to maintain a healthy environment for your aquatic inhabitants. For plant cycling, continue to monitor water parameters and maintain a balanced nutrient level to support plant growth. Plant as heavily as you are able and ensure they have adequate light and nutrients. This will help establish a harmonious aquatic ecosystem and contribute to the cycling process.
  5. Enjoying Your Cycled Aquarium: Congratulations! You've successfully cycled your new aquarium. Now, it's essential to maintain it with regular water changes, continued testing, and proper feeding. Regular maintenance ensures the health and happiness of your fish and plants.


If you’re looking to establish a healthy environment for your aquatic life, it’s important to understand the difference between cycling and seasoning an aquarium tank. Check out our blog post titled Cycling vs. Seasoning an Aquarium’ for more information on the topic!.

Cycling your new aquarium is like laying the groundwork for a vibrant underwater world. Pick fishless or fish-in cycling, follow the steps, and build a strong bacterial community that keeps things clean for your fish and plants to thrive.

Just a heads up, make sure to know your fish and plants' needs before they dive in. With a little love and care, you'll have an amazing aquatic showcase. Enjoy taking care of your aquatic buddies!

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