How to Cycle a 30 Gallon Aquarium

Cycling is the process of establishing the nitrogen cycle in your aquarium. The nitrogen cycle converts the toxic ammonia created by fish waste and decaying organic matter into a much less harmful chemical that can be easily removed by performing regular water changes. Cycling a fish tank is one of the most important steps in setting up a new aquarium.

Things You'll Need

  • Fully set up aquarium
  • 1 cup aged aquarium gravel
  • Ammonia neutralizing chemicals for aquariums
  • Measuring cup
  • 1 cheap fish
  • Fish food
  • Ammonia test kit for aquariums
Show More

Instructions

  1. Cycling the Tank

    • 1

      Add the cup of aged aquarium gravel from an existing, well established healthy aquarium. This can be obtained from a friend with a fish tank or you can buy a cup of aged gravel from a display tank in a fish store.

    • 2

      Add the manufacturer's suggested dose of ammonia neutralizing chemicals as stated on the side of the packaging. The amount you need varies greatly depending on which brand you choose. You can buy the chemicals at any fish supply store.

    • 3

      Float the fish in the bag it came in for 15 minutes to acclimate it to the water temperature.

    • 4

      Open the bag and add about half a cup of tank water to the bag.

    • 5

      Wait 10 to 15 minutes and add another half cup of tank water to the bag. Repeat this step of adding water half a cup at a time until you have doubled or tripled the amount of water in the bag. Do not rush this step.

    • 6

      Release the fish into the aquarium.

    • 7

      Feed the fish very sparingly for the next four to six weeks. Feed only once a day with only as much as the fish can eat within two minutes. Uneaten food breaks down quickly adding excess ammonia that will make cycling take longer and possibly injure or kill the fish.

    • 8

      Test the tank water with the ammonia test kit four weeks after adding the fish. If it reads zero, cycling is over and you can start adding fish one or two at a time over the next several weeks. At this point start regular maintenance. If the test reads anything other than zero wait longer. Test every few days until no ammonia is present before adding more fish and beginning maintenance.