Starting A Freshwater Aquarium | Cycling a New Aquarium

Freshwater fish aquarium in living room

Starting a new freshwater aquarium can be a wonderful experience, but it's important to understand the process of cycling your tank before adding any fish. Cycling your aquarium is essential for establishing a healthy environment for your fish to thrive in. It's a natural process that involves establishing a colony of beneficial bacteria in the tank that converts harmful ammonia into nitrite and then nitrate, which is less toxic for fish. In this blog post, we will explore the different ways to cycle a new freshwater aquarium quickly and effectively, including using ammonia, fish food, filter media, live gravel, plants, and moss. We'll also share some tips on how to maintain your tank during the cycling process and ensure your fish are healthy and happy. So, let's dive in!

There are three well known methods to cycle your fish tank:

1. Ammonia (Duration 4 to 8+ weeks)

One of the most popular and effective ways to cycle a new aquarium is to add pure ammonia to the tank water. You can purchase pure ammonia from a hardware store or use ammonium chloride from a fish store. Add enough ammonia to raise the ammonia level to around 4 ppm (parts per million). Test the water regularly to monitor the levels of ammonia, nitrite, and nitrate. The best test kit to use is the API Master Test Kit.

pure ammonia in a bottle

2. Fish food or a piece of raw shrimp (Duration: 4 to 8+ weeks)

Another way to cycle an aquarium is to add a small amount of fish food or a piece of raw shrimp to the tank. As the food decomposes, it will produce ammonia, which will start the nitrogen cycle.

photo of a cooked shrimp

3. Using filter media and gravel from an established tank (2 to 4 weeks)

If you have an established aquarium, you can use some of the filter media or gravel from that tank to seed your new aquarium with beneficial bacteria. This will jump-start the cycling process since the filter and gravel already have some of the good bacteria. You can add one hardy small fish to the tank right away. Test water parameters daily to ensure that the ammonia levels remain 0. If your ammonia levels rise, perform a partial water change and dechlorinate with Seachem Prime, which neutralizes chlorine, chloramine, ammonia. It's the best water conditioner for cycling a fish tank!

After a week, you can add a 1 to 2 more fish and continue to test the water daily for ammonia. You can add a few more fish every week until you reach the maximum your tank can hold.

The rule of thumb is 1 inch of fish per gallon of water. 

graphic of 1" of fish to gallon of water

4. Using "live" gravel, plants, and moss, and soil (2 to 3 weeks)

Another option is to use "live" gravel, plants, and moss that have already been colonized by beneficial bacteria. Add 3 tbs of high quality potting soil to a fine mesh filter sock and add to the the tank. Remove after 2 to 3 days. The combination of live gravel, plants, moss and soil will promote plant growth and provide a good source for the beneficial bacteria.

After a week, you can add one small hardy fish, like a betta. However, you should perform daily partial water changes of 1/4 to 1/3 of the tank using a dechlorinator like Prime, which will reduce the ammonia levels in the tank.

For all of these methods, you can increase the temperature of the water to around 80 degrees Fahrenheit, which will encourage the growth of beneficial bacteria.

ammonia level results new fish tank
After introducing my new betta in the fish tank, the ammonia levels rose to .25 ppm.
I performed daily water changes using Prime, and by the end of the 2nd week, the tank was cycled.

My fish tank's water parameters: Nitrite 0 and Nitrate under 5 PPM after 3 weeks.
Frequent partial water changes keeping organics low

Nano Aquaponic Fish tank update: week 3

API Quick Start

I also recommend adding API Quick Start to any of the 4 methods of cycling a tank. API Quick Start contains beneficial bacteria that your aquarium needs to start the nitrogen cycle. Shake the bottle really well before dosing. 

I am skeptical of the claim that API Quick Start allows you to add fish immediately to a new aquarium. Bacteria need time to establish in the aquarium and adding fish before the aquarium is stable will risk the lives of your treasured fish.    

Cycling Complications

Cloudy Water and Slime

During the first few weeks of cycling your aquarium, your aquarium may experience cloudy water or bacteria sludge buildup. This is normal and is caused by a bacteria bloom. To remove the sludge, you can wipe down the filter outlets with a soft cloth, but do not clean the filter media. You can also remove chunks of bacteria from plants and decor by giving them a wipe in a bowl filled with tank water.

If the filter media is clogged with slime, rinse in a bowl filled with tank water, and agitate just enough to remove the slime and return to the filter.

Ammonia Spikes

To ensure that your fish are not exposed to harmful levels of ammonia, feed lightly once a day, and perform ammonia tests daily using an accurate test kit like the API ammonia test. If the ammonia levels are above 0, perform a partial water change (using Prime again) and continue testing daily until the levels are at 0. You may need to perform partial water changes daily.

Once your tank is fully cycled, you can start feeding your fish normally and enjoy watching them thrive in their new home.

Aquarium Supplies 🐠🐟🐡

Back to the Roots Aquarium:

I recommend:
Aquaclear 50 filter for 15 to 28 gallon tanks: 

Live gravel:
Ceramic grow media:

Water Quality:
Water polishing filter: 
Fine mesh filter sock:
API water test kit: 
Seachem Prime water conditioner:
Almond leaves: 
Aquarium gravel vacuum and water changer:

What I feed my betta:
Hikari baby pellets:
Frozen mysis shrimp

More Reading 📚📖📗 
fish swimming through book graphic