How to Cycle a Saltwater Tank: A Guide for Newbies

A successful saltwater aquarium needs an established and balanced nitrogen cycle to maintain the health of its inhabitants. And we'll help you learn how to cycle a saltwater tank for the first time. Then you'll be set to add fish and monitor your aquarium to make sure the nitrogen cycle stays in balance.

If you're new to saltwater fish tanks, no need to worry. It'll all go swimmingly if you follow these simple steps. Just remember that patience and letting your aquarium settle slowly usually lead to the best conditions for healthy fish. 

The Nitrogen Cycle

Basically, a balanced nitrogen cycle means having the right amount of beneficial bacteria working to break down your fish's waste and uneaten food to neutralize chemicals like ammonia and nitrites that can kill your fish. Achieving a balanced cycle differs depending on whether your aquarium is new or you have fish living in it. 

Before you add any fish to your aquarium, you need to get the nitrogen cycle working properly and ensure it's balanced. While this process takes just a couple of days for a freshwater aquarium, it can take four to six weeks for a new saltwater aquarium. Taking time to ensure it's right pays off — it will make maintaining a balanced cycle much easier once you add fish to your aquarium.

Not Too Clean! Introduce Good Bacteria into A New Aquarium 

A brand-new aquarium is too pristine for fish. Your fish need a more natural environment — and that includes bacteria. However, you want the good kind of bacteria that cause your nitrogen cycle to work properly.

Start by introducing beneficial bacteria into the tank, a process called "seeding." At the same time, you want to create the conditions for the bacteria to spread throughout the tank. You have options, such as adding a little "live sand" or "live rock" (which is already permeated with bacteria) to your sand or gravel substrate. You can also add bacteria in liquid or solid form. 

Coralife Pure is a time-released ball of beneficial bacteria that integrates into your aquarium. With a brand new saltwater tank, add two Pure balls for every 30 gallons of water. Then each week, add a new ball per 30 gallons to keep your aquarium water clear and well-balanced. The balls will also help make routine cleaning and maintenance easier. Encourage beneficial bacteria growth by adding a Coralife Filter Bio-Ball to the filter.

Kickstart the Cycle by Adding Ammonia, Then Check to See if the Nitrogen Cycle Is Working

A day or so after seeding your aquarium with beneficial bacteria, add ammonia to the tank to encourage the nitrogen cycle to start. The easiest way to add ammonia is by sprinkling a little fish food onto the water every two weeks. Since you don't have fish yet to eat the food, it will slowly decompose and feed the bacteria you're trying to encourage.

At this stage, you want ammonia to form. You don't have fish in your tank, so the ammonia won't harm them. Track how the ammonia levels progress with the Aqueon Ammonia Aquarium Test Strips.

Keep testing your aquarium water with the Aqueon 7-in-1 Aquarium Test Strips to see how the nitrogen cycle progresses. At first, your ammonia levels will rise. Once nitrite begins to form, ammonia will start to fall again. Next, nitrates will appear — indicating beneficial bacteria are present and your nitrogen cycle is working — and then your ammonia and nitrite levels should fall back to zero. It takes between four and six weeks to establish the nitrogen cycle and ensure it's working well.

Tip: Keep aquarium lights off while cycling the water for the first time. Excess light can prompt too much algae growth until your bacteria levels are properly balanced. 

Monitor Carefully Before and After Adding Fish

Before you add any fish to your aquarium, test your water over several days to confirm your ammonia and nitrite levels remain at zero and your nitrate levels are no higher than 25 mg/L.

It's best to introduce just one or two fish at a time into a new saltwater aquarium (you can turn your aquarium lights on now) and wait at least two weeks for your tank to stabilize again. The food you provide and the waste your fish produce will alter the levels of bacteria and chemicals in your aquarium water. Monitor the water — and therefore the nitrogen cycle — closely to know how to react to the inevitable changes in the water's clarity and chemistry.

When you're just starting out, use test strips every two to three days. You want to ensure the beneficial bacteria are quickly converting toxic chemicals into safer ones and you don't have dangerous spikes of ammonia or nitrite. Take care not to overfeed your fish because their uneaten food gets converted to ammonia.

Every time you add a new element to your tank, like a water refresh or new fish, it affects the balance of bacteria and chemicals. Make changes gradually, and test your water at least weekly so your fish — and the beneficial bacteria sustained by the nitrogen cycle — will stay healthy. Over time, you will learn how your aquarium reacts to changes and might be able to test less frequently.

Simple Start for Saltwater Rookies

Cycling a saltwater tank isn't out of your depth, even if you're a saltwater aquarium newbie. An easy way to get started with a saltwater aquarium is with the Coralife BioCube Aquarium. It has the essentials to get you started, including LED lighting that's important for healthy fish, plants, and corals; a built-in filtration chamber; and a quiet pump. With the Coralife SMART BioCube Jr., you can control the lighting via the Aqueon BlueIQ app on your smartphone, plus get tips and set up maintenance reminders.

Add saltwater to the tank (you can mix your own with the Coralife BioCube Marine Salt) and follow the steps above to ensure your nitrogen cycle performs properly. Then you'll be set to add the fish of your choosing.

Understanding how your aquarium's filtration system, refreshing the water, and adding fish all affect the nitrogen cycle will help keep your fish healthy and reduce the amount of work needed to maintain your aquarium.

To learn more about water testing, check out Importance of Water Testing in Saltwater Aquariums. And when you're ready to dive in for more, be sure to read Getting Started with Saltwater Aquariums: Setting Up Your First Reef.