How to Cycle Your Saltwater Aquarium With Live Rock

Prepare Your Saltwater Aquarium for Use

Live rock aquarium
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New aquariums must go through a cycling process before any fish can be safely added to the environment. This process leads to the birth of the aquarium's biological "bacteria" base. From start to finish, this cycle usually takes around 30 to 45 days to complete, and depending on each individual aquarium's set up and care variables, sometimes longer.

If you don't want to wait around for nature to run its course and create this needed end result bacteria, there are ways to help speed up the cycling process by "seeding" a new tank with mediums or materials that already have a mature bacteria population established on them. Seeded live rock is an excellent source of bacteria and due to its porosity, it can carry a huge quantity of bacteria that will be buried in all of the nooks, crannies, and minute holes in the rock.

A biological bacteria seeding method will help to cut a substantial amount of time (weeks, in most cases) required to establish the biological filter in a saltwater aquarium, which is considered to be "cycled" when two different forms of bacteria (nitrobacteria and nitrosoma) are present in quantities that will process the ammonia (NH3) into nitrites (NO2) and then into nitrates (NO3), leaving no detectable nitrites. 

Hermit crab
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Before You Begin

It takes a saltwater tank much longer to cycle as opposed to a freshwater tank. Keep in mind you'll want to allow for at least six weeks for your tank to cycle before purchasing or adding fish. It's important to monitor and test your water often throughout the cycling process so you can properly time when you're ready to add your fish.

What You Need

Gather the following items when you're ready to cycle your saltwater tank:

  • A new saltwater tank fully set up with all desired contents except for the fish. This includes your filtration system, heater, thermometer, decorations, plants, and other accessories.
  • A seeding source such as live rock or media from another saltwater tank. Your other option is to use a bottle of pure ammonia. If using ammonia, make sure that it does not include perfumes or surfactants (detergents).
  • An aquarium testing kit to monitor the amounts of ammonia, nitrites, and nitrates in your tank's water.

Locate the Seed Sources

Seed sources are usually obtained by removing them from another saltwater aquarium that is well established. Ideally, the seed source should be at least six months old. It should also be disease free, meaning that it is not suspected of having a disease or is undergoing treatment for a disease of any kind. Good sources for seeded live rock are a local fish store, if rock that has been in a functioning saltwater aquarium is available, or a friend's tank that has been running for a period of time.

Transfer Live Rock From One Tank to Another

When transferring the live rock from the established tank, many people will scrub the rock to remove any algae and dead or decaying material. While removing as many unwanted "hitchhikers" (such as bristleworms or mantis shrimp) as possible is a good idea before transferring the rock, it is usually best to not scrub the rock to remove all of the algae as this will remove a lot of the beneficial bacteria, which will defeat the purpose of using the seeded rock.

Other tank materials such as live sand or sand substrate or even aquarium decoration from another established saltwater aquarium can also be used to transfer live bacteria and establish the biological filter bed in a new tank. These materials will carry the same bacteria as the live rock and will help cut the cycling time of the new tank. 

Nurturing Live Rock in Your Tank

Once the live rock is transferred to the new tank, the bacteria will require a food source (ammonia) in order to reproduce and populate the surface areas in the tank. While it is safe to place a few fish in the tank to provide the ammonia source, it is best not to load up the system with livestock too quickly as this will produce more ammonia than the relatively small population of bacteria can immediately handle.

There are a number of other sources for the ammonia required to feed the bacteria, other than just fish. Invertebrates such as hermit crabs, true crabs, and shrimp that you are planning to add to the tank will consume food and produce ammonia. Just placing these Reef Tank Safe Janitors in the tank ​will go a long way toward reducing tank maintenance in the future.

Using Ammonia to Cycle Your Saltwater Tank

If you don't want to use media from another tank or don't have access to a natural seeding source, you can also start the cycling process by adding drops of pure ammonia to your tank. To make sure there are no detergents in your ammonia, shake the bottle before using. If bubbles start to foam after shaking, it means detergents are present and you'll want to find an alternative ammonia source that's pure. Once you have secured an unadulterated bottle, add five drops a day for every 10 gallons of water to your empty tank to start the cycling process. When your test kit starts to show nitrites, cut back to only three drops a day.

Once the tank has reached its peak readiness, meaning your test strip reads zero ammonia and nitrites, and nitrates above 1 ppm, you'll want to stop adding ammonia. After you stop adding ammonia, wait at least three days before you add your fish. Both ammonia and nitrites can kill fish, so you want to be sure they are completely removed from the water before you add fish to that tank.

Preventing Problems With Your Tank During the Cycling Process

Testing the aquarium water for ammonia, nitrites, and nitrates on an almost daily basis will help you to determine how well the bacteria population is increasing as you go along. If the ammonia levels are rising too quickly and approaching the danger zone, you can quickly reduce the levels with a dose of an ammonia removal product such as Amquel to keep the level in the safe zone.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.