Cycling an aquarium is one of the most important steps when setting up a new aquarium. Before fish or other aquatic animals are introduced, the aquarium needs to develop a healthy biological filtration system capable of processing waste.
A properly cycled aquarium provides a much more stable environment for fish and helps reduce the risk of dangerous ammonia and nitrite levels.
At Aquassi Ltd, we recommend taking the time to establish the aquarium properly rather than rushing to add livestock. Patience during the cycling process can make a significant difference to the long-term health of your aquarium.
What Does Cycling an Aquarium Mean?
Aquarium cycling refers to establishing colonies of beneficial microorganisms within the aquarium’s biological filtration system.
Fish and other aquatic animals produce waste. Organic matter can also break down and release ammonia. Ammonia is highly toxic to fish.
Beneficial bacteria help convert ammonia into nitrite and then nitrate through the nitrogen cycle.
The basic process is:
Ammonia → Nitrite → Nitrate
Nitrate is considerably less toxic than ammonia and nitrite at appropriate concentrations, although it still needs to be managed through regular maintenance and water changes.
Why Is Aquarium Cycling Important?
A new aquarium does not immediately contain enough beneficial bacteria to process the waste produced by fish.
Adding fish too quickly can therefore result in ammonia and nitrite accumulating in the water.
High levels can cause serious stress and may be harmful or fatal to aquatic animals.
Cycling the aquarium before adding livestock allows the biological filtration system to become established first.
What You Need to Cycle an Aquarium
Before beginning, you should have suitable aquarium equipment in place.
This normally includes:
- Aquarium
- Filter
- Suitable biological filter media
- Water conditioner where required
- Aquarium test kits
- Heater where appropriate
- Thermometer
- An ammonia source for fishless cycling
A liquid test kit capable of measuring ammonia, nitrite and nitrate is particularly useful because it allows you to monitor the progress of the cycle.
Fishless Cycling
Fishless cycling is generally the preferred approach for establishing a new aquarium because it avoids exposing fish to potentially dangerous ammonia and nitrite levels.
Instead of using live fish to produce waste, an appropriate ammonia source is added to provide food for the developing bacterial population.
The aquarium filter should be running continuously so that water passes through the biological media.
Step 1: Set Up the Aquarium
Set up the aquarium completely before starting the cycle.
Install the substrate, hardscape, plants, filter and heater where appropriate.
Fill the aquarium with appropriately treated water and switch on the filtration system.
If you are creating a planted aquarium, plants can usually be introduced during the cycling process.
Step 2: Add an Ammonia Source
A controlled ammonia source can be added to begin feeding the developing biological filtration system.
It is important to use a product intended for aquarium cycling and follow its instructions carefully.
Avoid household cleaning products or unknown sources of ammonia, as these may contain additional ingredients that are unsuitable for aquariums.
Step 3: Test the Water
Testing is essential throughout the cycling process.
Regularly monitor:
- Ammonia
- Nitrite
- Nitrate
- pH
Initially, ammonia will rise as the aquarium receives its ammonia source.
As the first group of beneficial microorganisms becomes established, ammonia should begin to decline while nitrite increases.
Later, another bacterial population develops and converts nitrite into nitrate.
Step 4: Understand the Nitrogen Cycle
The nitrogen cycle can appear complicated, but the basic principle is straightforward.
Ammonia is produced first. Bacteria then convert ammonia into nitrite.
A second group of microorganisms converts nitrite into nitrate.
Nitrate can then be managed through water changes, plant uptake and other appropriate aquarium maintenance practices.
The aim of cycling is to establish enough biological filtration to process the aquarium’s expected waste load.
Step 5: Be Patient
Cycling an aquarium is not an overnight process.
The length of time required can vary depending on factors such as temperature, pH, filter media, ammonia source, bacterial populations and the aquarium’s individual conditions.
Do not rely solely on a fixed number of days.
Instead, use water testing to determine when the biological filtration is sufficiently established.
Step 6: Confirm the Cycle
A properly cycled aquarium should be capable of processing an appropriate ammonia source without leaving dangerous ammonia and nitrite levels.
Your test results should show that ammonia and nitrite are being processed effectively, with nitrate being produced.
The exact testing procedure should follow the instructions for your chosen cycling method and test kit.
Only introduce livestock when the aquarium is ready and water parameters are appropriate for the species you intend to keep.
Step 7: Perform a Water Change
Once the cycle is established, a suitable partial water change can help bring nitrate and other dissolved substances to appropriate levels before livestock are introduced.
Use appropriately treated replacement water and avoid making unnecessary dramatic changes to water chemistry.
Adding Fish After Cycling
Once the aquarium is ready, introduce livestock gradually rather than adding a large number of fish immediately.
Adding too much livestock at once can place a sudden demand on the biological filtration system.
Allow the aquarium to adjust and continue monitoring ammonia and nitrite after new fish are introduced.
If either rises significantly, take appropriate action immediately.
Do You Need Beneficial Bacteria Products?
There are commercially available products designed to introduce or support beneficial microorganisms.
Some aquarists use these products when establishing new aquariums, but their effectiveness can vary depending on the product and conditions.
They should not be considered a substitute for testing and proper aquarium management.
The safest approach is to monitor the actual water parameters rather than assuming that an aquarium is cycled simply because a bacterial product has been added.
Can You Cycle an Aquarium With Fish?
It is possible to establish biological filtration while fish are already present, but this can expose them to ammonia and nitrite.
For that reason, fishless cycling is generally preferable when starting a new aquarium.
If fish are already present in an uncycled aquarium, ammonia and nitrite should be monitored closely and appropriate water changes and management should be undertaken to protect the livestock.
Cycling a Planted Aquarium
Planted aquariums can also be cycled before fish are introduced.
Aquatic plants can absorb certain nitrogen compounds and contribute to the overall ecosystem, but plants do not eliminate the need for biological filtration.
A planted aquarium still needs an appropriately established filter and stable water conditions.
Common Aquarium Cycling Mistakes
Several mistakes can make cycling more difficult.
One common mistake is adding fish before the cycle is complete. Another is replacing all biological filter media at once, which can remove a significant portion of the established bacterial population.
Over-cleaning filter media with untreated tap water can also damage beneficial microorganisms.
Whenever possible, follow the manufacturer’s instructions for maintaining filter media and use suitable aquarium water during cleaning.
How Aquassi Ltd Can Help
At Aquassi Ltd, we can help you establish an aquarium correctly from the beginning.
Our aquarium services can include aquarium design, installation, aquascaping, equipment selection, water testing advice and ongoing maintenance.
Whether you are establishing a small nano aquarium, planted aquascape, community aquarium or specialist display, getting the biological foundation right is essential.
Build a Healthy Aquarium From the Start
Cycling may require patience, but it is one of the most worthwhile things you can do when establishing a new aquarium.
By allowing beneficial microorganisms to develop, monitoring ammonia, nitrite and nitrate, and introducing livestock gradually, you can create a much more stable environment for your aquatic life.
Aquassi Ltd – bespoke aquascaping, planted aquariums and professional aquarium services.
If you are setting up a new aquarium and need help with cycling, aquascaping, installation or maintenance, contact Aquassi Ltd to discuss your requirements.