How to cycle a fish tank and why it’s so important
Preparing a new fish tank is an exciting experience, and it can be understandably tempting to add your new fish to their tank as quickly as possible. However, such a hasty introduction can be deadly for fish, especially if your tank water is not safe or habitable for aquatic life.
Fish tank cycling is the process of bringing your tank water conditions to a safe, healthy level for fish. It is crucial for establishing good bacteria, ensuring your water has the essential qualities for fish survival.
While carrying out a fish tank cycle can initially seem daunting, the process is easy once you know the basics. Read on to learn how to cycle a fish tank, including how long it takes and why it’s so important!
Table of contents
- What is a fish tank cycle, and why is it important?
- What happens during a fish tank cycle?
- How to cycle a fish tank
- How long to cycle a fish tank
- Shop fish tank essentials at Pond Planet
What is a fish tank cycle, and why is it important?
A fish tank cycle is the most crucial element in preparing a safe and habitable environment for fish, especially if you’re setting up a new fish tank from scratch. It includes bringing the tank water conditions to a safe, healthy level for aquatic life and establishing good bacteria that help break down toxic waste products and convert them into less harmful chemicals.
In the natural world, fish don’t live in crystal-clear tap water. They thrive in ecosystems made up of plants, other animals and bacteria. The same applies to your pet fish, and cycling their fish tank or aquarium is the way you can ensure their water has the qualities they need to survive.
The nitrogen cycle in a fish tank
Cycling refers to the nitrogen cycle, which, regarding fish tanks and aquariums, means the process of establishing good bacteria in your tank water for fish to survive.
As fish waste breaks down, it naturally releases ammonia into the tank water, which is toxic to fish if left untreated. So, good bacteria are needed to convert them into less harmful nitrite and then nitrate. Brand new fish tanks do not have this good bacteria, which means fish cannot survive.
A functional ecosystem in your tank takes a while to develop, which is where cycling comes in. With this in mind, you must wait to buy tropical fish until your aquarium is ready – and never attempt to cycle your tank water with your fish already in it.
What happens during a fish tank cycle?
The fish tank cycle, also known as the nitrogen cycle, includes three different stages:
- Ammonia is released into the tank water
Ammonia is naturally introduced into the fish tank water as fish waste, dirt, and debris break down. This is toxic for fish in high concentrations and can be deadly if left untreated.
- Bacteria forms and converts ammonia into nitrite
Good bacteria begin to form, converting ammonia into nitrite. Nitrite is still toxic to fish. However, this is an important stage of the nitrogen cycle.
- Nitrite is converted into less harmful nitrate
During this final step, nitrite builds up and is converted into nitrate by new bacteria. Nitrate is not harmful to fish except in extremely high concentrations, so it’s essential to regularly check the water conditions to ensure they remain safe for fish.
How to cycle a fish tank
So, how do you cycle a fish tank? Here, we cover the simplest and most effective ways to cycle your fish tank for beginner and advanced fish keepers.
Method one: In-fish cycling
In-fish cycling is one of the most popular fish tank cycling methods. It refers to the process of keeping only a couple of resilient fish species in the tank at the beginning and slowly increasing the number as you complete the nitrogen cycle.
Step one: Set up your fish tank
First, set up your new aquarium with your chosen plants, rocks and filtration system. Living plants absorb nitrate which makes them a great long-term addition for an aquarium.
Step two: Add your fish
Introduce a few fish to your tank. At this stage, it’s essential only to add hardy fish that can survive the initial high toxin levels before the good bacteria can grow.
Step three: Lightly feed your fish
Feed your fish very lightly, to begin with, aiming for once every other day. Ensure you don’t overfeed your fish, as excess food and fish waste contribute to ammonia levels, making tank water more toxic.
Step four: Change the water periodically
Every few days, replace approximately one-quarter of your tank’s water to ensure toxin levels do not rise too high for your fish to survive. This is key to creating optimum water conditions without killing the fish! If you have an existing tank, you can speed up the tank cycling process by adding filter media from your existing aquarium to your new tank to help spread good bacteria.
Step five: Test the tank water
Using an aquarium test kit, check your tank water every few days to measure the levels of ammonia and nitrite present. If they reach above 0.2 ppm, do an immediate partial water change.
Once the ammonia and nitrite levels in your tank are undetectable or as close to zero as possible, you can gradually add the rest of your fish in stages, following the same process as above. The cycling process is complete when all your fish can feed normally, and toxin levels stay at zero because the good bacteria is doing its job.
Method two: Plant Cycling
Plant cycling is an effective and natural method of introducing good bacteria to tank water. However, it is only ideal if you have your tank for a while before you get your first fish, as the cycling method can take about 6 weeks when done naturally.
For this method, introduce live aquarium plants to your aquarium before any fish. This will naturally encourage the growth of good bacteria and create a natural ecosystem for fish to live.
After around 4-6 weeks, the nitrogen cycle should be complete, meaning it is safe to introduce a few fish. When the nitrogen cycle is complete in your tank, you’ll know when your aquarium plants start to produce new growth, which means they are converting toxins into new leaves.
You can start adding your fish at this point and follow the same steps as in-fish cycling: feed them sparingly at first and test the water to check that ammonia and nitrite levels are low enough.
Method three: Fish food cycling
Another easy way to cycle your fish tank is to add a small amount of fish food to the water each day. Like fish waste, the food will naturally release ammonia into the tank water as it breaks down.
Do this for about a month, using aquarium test kits to monitor the ammonia, nitrite, and nitrate levels. As the good bacteria develop, the ammonia and nitrite levels will start to decrease, and nitrate levels will climb to a safe level for fish.
Though you might feel impatient to add fish to your new tropical set-up, it’s important to take the time to allow the tank cycling process to complete, as not doing so could cause nitrate poisoning or ‘New Tank Syndrome’, which can be fatal for fish.
How long does it take to cycle a fish tank?
Fish tank cycling has no specific time limit, as the time it takes to complete depends on various factors. Generally, the process can take between six to eight weeks. However, there are two clear identifiers you can look out for to know when your cycle is finished:
- Your tank’s ammonia and nitrite levels have remained at zero for two weeks.
- Your tank or aquarium can go for two weeks with only once-a-week partial water changes.
Watch for these signs, and you’ll know whether your cycle is complete! If you add more fish or change your tank’s ecosystem, check your ammonia and nitrite levels to ensure your fish can survive and thrive.
Shop fish tank essentials at Pond Planet
Fish tank cycling is crucial to setting up any aquarium, and forgoing this step can be deadly for aquatic life. While the process may seem daunting to beginners, it’s easy once you know the basics.
Pond Planet offers everything you need to successfully set up your fish tank, from aquarium starter kits to aquarium decor, fish food, and more. Shop our aquarium supplies collection to discover fish tank essentials by industry-leading brands, and begin your fishkeeping journey today with Pond Planet!
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