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Cycling a New Fish Tank

Updated on February 16, 2012
Zebra Danios are very hardy fish and are an excellent choice for establishing a bio-cycle in a new aquarium.
Zebra Danios are very hardy fish and are an excellent choice for establishing a bio-cycle in a new aquarium.

What is New Tank Syndrome?

New Tank Syndrome refers to what happens to a newly established aquarium for the first 6 to 8 weeks while it is establishing a biological filter or bio-cycle. When a fish tank is first set up and some fish are placed in the tank, the water they are living in is fresh water usually from a faucet in the home. The new tank will be decorated with new aquarium d├ęcor and gravel probably purchased at the same time that the fish tank was. As the new fish begin to live in the new tank they will eat and produce waste which releases toxins into the water These toxins are very poisonous to fish. As the level of toxins increase in the water it will become harmful to the fish and even fatal. This is why many fish will die in the first few days after being placed in a new aquarium.

New Tank Syndrome happens to all new aquariums. It is something that every aquarium fish keeper will experience. By learning about what it is and why it happens, a new aquarium owner will be able to know what the solutions are for handling new tank syndrome..

Cycling a Fish Tank with Fish

One solution is to buy a couple hardy tropical fish to start in order to establish the biological cycle in the new aquarium. Hardy fish are fish that are tougher and can tolerate the higher amounts of toxins that are present in the aquarium while it is cycling. Even though these fish are hardy, it is important to preform partial water changes to keep the toxin levels in the water down while the tank is cycling. Hardy fish I suggest for cycling a tank are...

  • Zebra Danios
  • Female Guppies
  • Scissor-Tail Rasboras
  • Silver Mollies
  • Blue / Opaline Gourami
  • Gold Gourami

Cycling the New Tank

The Nitrogen Cycle also called the Biological Cycle is a cycle that all new aquariums must establish to be able to provide a healthy living environment for the fish that will live in the tank. Cycling a fish tank is giving the new tank the time it needs for the nitrifying bacteria to grow. New tanks lack the bacteria needed to break down the toxin produced by the waste products from the fish.

The cycle starts with the fish releasing waste products into the water. These products produce ammonia, which is very toxic to fish. As the ammonia level in the water increases some new bacteria will begin to grow in the tank. This bacteria will eat the ammonia and the ammonia level will then drop.

The ammonia eating bacteria produce another waste product that releases nitrite into the water. Nitrites are also very toxic to fish. As the nitrite level in water starts to increase another bacteria will then start to grow. This new bacteria will eat the nitrites causing the nitrites to drop.

The nitrite eating bacteria produce their own waste products which give of nitrates. Nitrates are not as toxic to aquarium fish. Even though nitrates are not as harmful they should not be allowed to build up in the tank. Regular partial water changes are needed to keep the nitrates low. Once there are nitrates in the water and the other 2 bacteria levels are remaining close to nothing the Nitrogen Cycle is completed and the tank has establish a biological filter.

Order a Complete Test Kit

API FRESHWATER MASTER TEST KIT 800-Test Freshwater Aquarium Water Master Test Kit
API FRESHWATER MASTER TEST KIT 800-Test Freshwater Aquarium Water Master Test Kit

This complete test kit offers everything needed to track ammonia, nitrites and nitrates. It also has chemicals needed to track other things like the pH level of the water.



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    • profile image

      jonospin 4 years ago

      Not all new tanks will experience "new tank syndrome". NTS describes an affliction caused by poor water quality. Poor water quality can be avoided whether the tank is new or old. I really don't like how this person recommends the use of live fish for cycling a tank. Just because a fish can handle having its eyes, body and fins burned by toxic chemicals, doesn't mean we should subject them to this. (google ammonia burn in fish)

    • profile image 5 years ago

      I purchased a new 10 gallon aquarium, gravel, an air pump,a water filtrator. and 2 KOI (oreo and calvin) it has been over 8 weeks and the tank is very cloudy. I have purchased API ACCU-CLEAR and did about 1/2 water change the fish are eating and are smiling... I AM NOT ! when will I get to see my fish ?

    • John Sarkis profile image

      John Sarkis 6 years ago from Los Angeles, CA

      Great hub Web Gazelle.... White Clouds are also a hardy aquarium fish.


    • Web Gazelle profile image

      Web Gazelle 7 years ago from USA


      If you are using the product called "Stress Zyme" and you add more than the directions state on the label then your aquarium water can become cloudy from a spike in bacteria or "bacteria bloom". Only add the amount that is stated on the label and once your tank is cycled there is really no need to continue to add Stress Zyme to the water. The directions tell you to add it with every water change but they tell you that so you keep buying the product.

      If you are using another product please let me know what you are using. You could get similar results with other similar products.

    • profile image

      ness 7 years ago

      Ok I started my 55 gallon take over. it seemed like when I put the water condition in the take it became cloudy..why is that...

    • profile image

      Fish Tank Betta 7 years ago

      Nice videos, liked these.

    • Web Gazelle profile image

      Web Gazelle 7 years ago from USA

      Don't do that large of a water change. That size of change could shock your fish even more and the additional stress could certainly kill them. Do partial water changes of 25% to 30%. Do one every day as needed to reduce the ammonia and nitrite levels.

    • profile image

      rhemity 7 years ago

      thanks heaps i did a 90% water changed killed my albino bristle nose sucker and my borneo suck and now my gibbiceps look stressed hope i don't loose any more am going to get plants to help the cycle along as i believe they will have some benefit to the tank and some objects from my other cycled tank to help cheers

    • Web Gazelle profile image

      Web Gazelle 7 years ago from USA

      A great way to "jump start" the cycling process is to transfer décor and/or substrate from an established aquarium to your new one.

      Be aware that the reverse is also true. Removing and replacing the décor and/or substrate in an established aquarium can have a negative impact on the biological cycle.

    • profile image

      Alan V. McClain 7 years ago

      I have just set up a tank to upgrade my old tank it contianed 8fish and 15 gallons of water. The pet shop guy told me that if I used new gravel, new filter, and new décor that my old water would transfer my bacterial filter. He was wrong, now my new tank(30gallons)has killled three of my fish, I had a high ammonia level a wich I was brought down with water changes, a rock bag n my filter, and Nutrafin Cycle. My ammonia levels are still a little high but but nitrites are off the charts. I wondered if there was a way to speed up the procees and save my fish, or at least make the environment live-able. I did find your information helpful I just really hope you can give me a little more.

    • adorababy profile image

      adorababy 7 years ago from Syracuse, NY

      It is important to note that the cycling process does not begin until fish are added. Some hobbyists set up their aquarium for weeks or even months before adding fish.

    • Katelyn Weel profile image

      Katelyn Weel 8 years ago from Ontario, Canada

      Great hub, I appreciate the concise information, you've made this cycling thing a lot easier to understand.