What to Do When Your Fish Tank is Not Cycling?

The nitrogen cycle in the fish tank must continue to run to maintain the ideal fish environment. However, if the fish tank isn’t cycling, a lot of ammonia will accumulate in the water.

Ammonia can hurt your fish since it is toxic. When different helpful bacteria break down the wastes generated by fish, a cycle is established.

I’m going to tell you how to sustain cycling properly in this article. To understand everything there is to know when the fish tank not cycling, read this article thoroughly.

Why isn’t the Nitrogen Cycling Inside Your Fish Tank?

If there are no bacteria present in the fish tank, the ammonia that the fish excrete does not cycle. Several factors contribute to the fish tank’s bacterial colony being considerably reduced or absent.

The following are the root reasons for this issue:

  • Adding a lot of ammonia without first checking the nitrite or ammonia levels.
  • You are trying to cycle without any fish. Ammonia cycles significantly more slowly as a result, giving the impression that the cycle has stopped.
  • The oxygen level in the water is low.
  • The tank’s bottom is devoid of any stones, grass, or marbles. Thus, bacteria are unable to adhere to the glass’s surface.
  • The testing kit’s reading, which indicates sluggish cycling, is incorrect.
  • Increased water circulation inside the fish tank prevents bacteria from growing into colonies.
  • You have poured untreated tap water inside the tank without deactivating the chlorine. The bacteria can’t live in chlorine water.
  • You have used too many ammonia-removing products in the water.
  • High nitrate and low nitrate levels.
  • The pH level of the water is lower than 7.
  • The bacteria that you may buy in bottles died because they were stored at temperatures that were either too high or too low.
  • The fish tank’s temperature is below 20 degrees Celsius.

What Are the Steps of Cycling a Fish Tank?

There are mainly three ways to cycle a fish tank. These are:

  • Fish-In Cycling
  • Fishless Cycling
  • Cycling with Plants

Fish-in Cycling:

De-chlorinate the water initially. Then you ought to begin by using fewer fish. The ideal ratio is one fish for every 45 litres of water.

The Pupfish, White Cloud Mountain Minnows, Zebra Danios, Barbs, and Platys are the greatest options for the process. Feed the fish less in the beginning. It should be sufficient to feed them three to four times each week.

You should replace the water every three days for the course of this procedure, which takes four to six weeks. Ammonia and nitrite levels can be maintained at the proper levels by making a 15 to 25 percent water change.

By introducing nitrifying bacteria or substrates from previous fish tanks, you may potentially accelerate the process. You must now use a testing kit to check the water’s ammonia content.

You should partially replace the water if you discover that the ammonia or nitrate concentration is more than 0.2 parts per million. At least once every two days, you should test the water.

You should begin putting more fish in the fish tank after approximately a week. You may only add a maximum of two fish every week.

Fishless Cycling:

Since it provides a suitable environment for every fish, this method is the safest. Add some fish food to the water to start. The food will then release ammonia inside the water.

Utilize the testing kit to test the water. You should keep adding the same quantity until the level reaches 3 parts per million. Make sure it doesn’t drop below 3 ppm.

Along with ammonia, you should begin checking the levels of nitrite and nitrate. The cycle has ended if the levels of ammonia and nitrite are zero and the amount of nitrate is more than 40. Now, you should slowly add fish into the fish tank.

Cycling with Plants:

The aquatic plants consume more ammonia compared to bacteria. Therefore, you may use plants to reduce the ammonia and nitrite level using the same method as fishless cycling.

The ammonia and nitrite will be converted into nitrate by the plants. The development of the plants ensures the procedure.

You can gradually add fish into the tank after testing and attaining a result of 0 ppm for ammonia and nitrite and 40 ppm for nitrate.

How to Continue the Process When a Fish Tank Not Cycling?

To stop the cycle from ending suddenly, you need to follow several rules. Follow these instructions precisely to prevent the fish tank not cycling:

  • Clean the Filter: Many materials and wastes have the potential to clog the water filter. The bacteria will thus grow gradually as a result. You must remove the sponge to clean the filter.

After that, clean the fish tank with water from the tank. Avoid cleaning it with tap water because doing so might make the cycle take longer. It is also suggested to use filters that have been utilized in other fish tanks.

  • Regulate the Temperature: It is important to make sure the water within the fish tank is at least 20 degrees Celsius. Depending on the size of the fish tank, you need to install either one or two water heaters.

    21 to 27 degrees Celsius are good for most fish and the cycle process. You should regularly check the water’s temperature and change it accordingly.
  • Maintain the pH Level: The water should have a pH between 7 and 8. Any value below 7 causes the procedure to become sluggish. You can inspect the pH level using water testing kits.

Use reverse osmosis or deionized water if the pH level is higher than optimal. Peat moss or driftwood can also be added.

If the pH level is lower than 7, you should add baking soda to the water. 5 millilitres of baking soda per 20 litres should increase the pH level significantly.

Which Tools Do You Need to Maintain the Nitrogen Cycle of Your Fish Tank?

You need a few tools for cycling the fish tank. Maintaining the cycle also requires few products. Take a look at my suggestions:

  1. Fluval Cycle Biological Enhancer, Aquarium Water Treatment
    – Safe for creating a biological habitat for fish inside fish tanks.
    – Easy to use in both saltwater and freshwater fish tanks.
  2. Eheim Jager Aquarium Thermostat Heater
    – Has power of 25, 50, 70, 125, 150, 200, 250, or 300 watts.
    – Automatic shutdown process if the water level drops too low.
  3. API Ammonia Freshwater and Saltwater Aquarium Water Test Kit
    – Can test the level of pH and ammonia in the water.
    – Provides freshwater, pond, saltwater, and reef test kits.
  4. Fluval Mopani Driftwood Aquarium Decoration
    – Helps to reduce the pH level of the aquarium water.
    – Approximately 4×10 inches with a sandblasted finish.
  5. TetraMin Plus Tropical Flakes, Cleaner Water Formula
    – Can be fed to all kinds of tropical fish and won’t make the water dirty.
    – Includes natural shrimp for flavor.


You must ensure that the fish tank has a nitrate concentration of at least 40 ppm, as well as low levels of ammonia and nitrite. The cycle should continue without interruption if the precise measurements are maintained.

I have discussed several potential causes for the fish tank’s slow nitrogen compound cycling.

Follow my guide to prevent the probability of the fish tank not cycling.

Related Posts:

Arif H Fahim

Welcome to PetFishTank! My name is Arif. I make an effort to publish educational articles using my many years of expertise as a fish owner.

Recent Posts