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Tips for Cycling Your New Aquarium

Getting Your Fish Tank Up and Running with Minimal Headaches

(The First Tank Guide)

What is Cycling?

Cycling your tank is probably something that you have never heard of unless you have been paying attention to the *.aquaria news groups, you have several friends with tanks, or you are working with a fairly good pet shop. The effects of the cycling process are sometimes referred to as "New Tank Syndrome," which can be deadly.

"Cycling the tank" means that you are establishing a bacteria bed in your biological filter to remove the toxins that the fish's metabolism creates. There are right and wrong ways to do this, and several things you can do to slow this process (which you don't want to do). There are two steps to cycling, but you don't have to do anything special for either of them. First, your filter will grow a culture of bacteria that digest ammonia and turn it into Nitrite (which is more toxic than the ammonia in hard water or water with a higher pH), then your filter produces bacteria that digest Nitrite and turn it into relatively harmless Nitrate. However, Nitrate will contribute to loss of appetite and stress in your fish, as well as contributing to algae growth, so it is important to do regular small water changes to keep your tank in best condition. Read more on water changes while the tank is cycling.

How Do I Cycle MY Fish Tank?

You should cycle your fish tank with a small number of fish. They should be hearty fish and a variety of fish that you want to have in your fish tank in the long run. Do not cycle your tank with lots of feeder goldfish. Do not cycle your tank with any goldfish unless you intend to keep goldfish. Unfortunately many pet shops still suggest this. If you want to know why, you could review my no goldfish page.

What Fish Should I Use to Cycle MY Aquarium?

For a tank of small community fish, White Clouds or Zebra Danios are good cycling fish; Cherry Barbs or Tiger Barbs are good for a slightly more aggressive tank; or Pseudotropheus zebra is a good choice for an African Cichlid tank. Your local pet shop should be able to point you toward some hardy fish of the type you are looking to keep.

Purchase a small number (the number will depend on the size of your aquarium and type of fish and -to a lesser degree- the type of filter) of these fish and introduce them to your Nitrogen Cycle Diagram tank. For a ten to twenty gallon tank, two or three small schooling fish or one small cichlid would be more than sufficient. Let the tank sit for a couple of days, feeding your fish carefully to prevent excess food from decaying and fouling the water. There are several reasons that you do not want to cycle your tank with a large number of fish, here are a few:

  1. Cycling a tank with many fish will produce a lot more waste, which will be stressful to your fish, resulting in higher die-off and greater susceptibility to disease.
  2. Cycling with a large number of fish will increase water problems incurred during the cycling process.
  3. Cycling with a lot of fish can contribute to a foul smell coming from the tank.

Every couple of days, do a 10%-15% water change, and after about a week, take a sample of your water to a fish store to get it tested. Most pet shops will test fresh water for a minimal fee, or even for free! If the store you got the fish from won't, check to see if there is another local store that will. At this point, your water should test with high ammonia and maybe a trace of nitrite. If it isn't, don't worry. Just give the tank time. The cycling process usually takes six to eight weeks.

After about eight weeks, your ammonia and Nitrite levels should be acceptable (about trace levels), and you can add more fish. Do not add more fish until the ammonia and Nitrite levels have both dropped. Remember to add new fish a few at a time to prevent over-stressing the filter. If you add too many at once, your tank will have to cycle again, yet if you add a few at a time, your bacteria growth rate will just increase for a short time, with minimal effect on your fish. There are other indicators that your fish tank has finished cycling.

What if I am Still Having Problems?

If, after six to eight weeks of cycling, your ammonia and nitrite levels aren't satisfactory (well, zero), you need to trouble shoot your situation.

Cycling the tank takes between two and eight weeks depending on several factors including:

What about Chemicals to Cycle My Aquarium Faster?

You should not need to use any chemical to stop unwanted increases in ammonia levels. Your biological filter should take care of that for you. If you have ammonia problems or see signs of ammonia stress after the tank has cycled, then your tank is overpopulated, under-filtered or overfed. Ammonia in the tank is a sign of a problem, not something that is easily treated with a chemical. Use of a chemical to remove ammonia will very often result in starvation of your biological filter leading to more ammonia problems and meaning that you will need to cycle the tank again. Remember, if your ammonia levels are high, you need to treat the problem that is causing the high ammonia levels, not the ammonia itself, which is just a symptom.

I recommend against using a bacteria booster or any kind of chemical when cycling your tank. These tend to leave you with a less stable tank in the long run. A tank cycled slowly and carefully with a few fish will usually cycle in six to eight weeks. A tank cycled with a bacteria booster or chemical supplements will take between two days and eight months to cycle, usually completing the cycle at about eight weeks, and these tanks usually do not stabilize for about six months after the last treatment. Do not use these products if you want a stable, easy to care for tank.

If you are just thinking about getting your first aquarium, you might want to start with some simple steps to a successful aquarium.

Check out these pages to help you get started with your first fish tank:



"The last time I wrote to you I [was] struggling with aquarium maintenance and dying fish. Now two years later I have been successful as ever and people wonder how I manage to keep my tank clean. I upgraded to a bigger 75 gallon tank last year. This is all thanks to your page."
April 16, 2012
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"I just wanted to thank you for your highly informative site. We just set up a fish tank and thought that we would get enough information from the pet store where we bought the fish to help us get it going correctly. We had no idea what we were doing and completely relied on the store employees (who have given us different stories every time we return)."
January 11, 2013
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