How to Cycle a New Marine Aquarium without Fish

Properly setting up a new marine aquarium is essential to the health of the fish you'll eventually add to it. One of the most important parts of new-aquarium setup is cycling your aquarium. Cycling an aquarium is when you begin the nitrogen cycle in your aquarium. This is done by maturing the filtration and creating aerobic bacteria in the aquarium, which will convert ammonia and nitrites -- which can poison fish -- into nitrates. Balancing this cycle and making sure it's working properly is the key to a healthy marine aquarium.

Things You'll Need

  • Live marine aquarium rock
  • Live marine aquarium sand
  • Ammonia or fish food
  • Water testing kits
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Instructions

    • 1

      Raise the water temperature in the tank to between 85 and 90 degrees Fahrenheit. These higher temperatures promote bacteria that aid in cycling.

    • 2

      Turn on all the filtration systems. Let the filtration systems work while the sand settles. Leave the tank alone for two to three days.

    • 3

      Add live rock to the marine aquarium. Live rock is full of microscopic algae and marine life that aid in the nitrogen cycle. Usually one or two pieces are enough live rock for the aquarium at this point.

    • 4

      Add a small amount of ammonia or fish food to the tank to start the cycle.

    • 5

      Test the water for ammonia. Use a water-testing kit. The ammonia levels will initially be high, but should balance and then decrease over a period of days. Test the water daily until the ammonia levels start to decrease.

    • 6

      Begin testing the nitrite levels in your marine aquarium after the ammonia levels start to drop. The nitrite levels will act in a similar way to the ammonia, rising, then balancing, and finally dropping.

    • 7

      Add more live rock when the nitrite levels begin to decrease. Adding more live rock will cause another spike in the ammonia and nitrite levels, but this disturbance should not last as long as the initial cycle.

    • 8

      Begin testing the water for nitrate levels. These levels will start low but should begin to rise slightly.

    • 9

      Continue testing the water daily for several weeks, letting the organisms on the live rock settle in and allowing the cycling to continue, balancing the levels in the marine aquarium.

    • 10

      Add live sand to the marine aquarium. This sand is very similar to the live rock and achieves a similar effect. Add sand according to the directions on the package.

    • 11

      Wait until the ammonia and nitrite levels read at zero and you see a low-level reading of nitrates. Slowly reduce the water temperature to one that is comfortable for the fish species you'll be introducing.