Successfully Cycling an Aquarium

Aulonocara sp Orchidea RedThere are several different approaches in successfully cycling an aquarium. Before we discuss these, please remember that the fish tank cycle is the most important step you must complete to have success in this hobby.

So many potential tropical fish keepers leave the hobby or give up because they repeatedly keep losing fish. The reason(s) for this mass exodus and frustration is due to tropical fish keepers:

  1. Not knowing about the fish tank cycle, or
  2. People rush fish tank cycling and do not allow for the cycle to fully run its course.

When cycling an aquarium you must make sure you have the most important item required for this process.

This item is patience.

So do you have this important item? If not, you need to find some fast! To cycle an aquarium, it takes on average 3-6 weeks. If you rush this step, you will have problems. You may lose fish, money, time, and energy! Please give the fish tank cycling process the time it needs.

How to Cycle A Fish Tank

Once you have everything setup and the water is stable, it is time for you to cycle your aquarium. The first step that will help speed this process up is for you to “seed” the aquarium.

“Seeding” an aquarium is the process of bringing in established beneficial bacteria from an established aquarium tank. By introducing an established bacterial colony, the time involved in cycling an aquarium is dramatically decreased.

Ways to seed your new tropical fish tank:

  • Use a filter cartridge, sponge, or other filter media from an established tank.
  • Fill a media bag, or a rinsed off pantyhose stocking with gravel from an established tank.
  • Use a few gallons of an established tank’s water in your tank.
  • Use decorations such as gravel, driftwood, and even artificial plants from an existing cycled tank.
  • Purchase live plants and put them in your new tank.

Please note that you should only use the above mentioned items from a disease free tank. If you suspect any illnesses in the other established tank, DO NOT seed your tank with anything from that tank.

Below you will see 3 Stages with the Average days it takes to run that stage of the cycle. The actual length of the cycle is influenced by many contributors. So therefore, some cycle times are longer than others.

Stage 1 (7-14 days)

First your aquarium must have a source of Ammonia to feed the much-needed beneficial bacteria. If you need to refresh yourself on the Aquarium Nitrogen Cycle, please do so.

There are several options available to introduce Ammonia into your aquarium. The first and most commonly used is introducing a few hardy starter fish. You will need to add 1 or 2 small tropical fish into your tank. These fish will begin producing waste (ammonia) and will give your bacteria colony a jump start.

Please do not feed them much or anything at all. Remember another form of ammonia is uneaten food. We want to introduce ammonia slowly.

On you second day, use your freshwater test kit and measure the ammonia in your aquarium water. Read the directions and compare the results to the chart included. If you show an extremely high level of ammonia, change 25-30% of your aquarium water.

On day three, repeat the process and test your ammonia levels. If everything checks out in the safe range of your test, you can feed the fish just a little bit of food. If ammonia is very high, perform a 25-30% water change.

Note - If your ammonia levels are excessively high, you may increase your water changes up to 50% or two water changes per day. Only do this if your ammonia is excessively high.

Stage 2 (7-14 days)

After 7-14 days of repeating this process of checking ammonia, water changes, and light feedings, you should start testing your nitrite. You will begin showing very little nitrite and then it will slowly start climbing up higher daily.

As long as your ammonia and nitrite levels are not in the “danger” zone, do not change any aquarium water. Feed the 1-2 fish in the tank very lightly. This process is key to make sure that the bacteria level is growing in order to convert nitrite into nitrate.

If your tests show dangerous levels of ammonia or nitrite, change 25-30% of your water and then test again. Towards the end of this stage, you will begin seeing nitrate levels showing up on your test results.

Stage 3 (7-14 days)

During this time, you should see very little if any ammonia and you may still show some nitrite. You should now start seeing significant nitrate levels. This is a great sign. This means that your nitrite is being broken down into less harmful nitrate.

When you test your aquarium water, you will notice increasing levels of nitrate. You can not perform a 25-30% water change. Test your water everyday for the next few days and ensure that nitrate levels do not accumulate too high.

After two consecutive days of water tests that show zero or very, very little ammonia, zero or very, very little nitrite and a acceptable level of nitrate, you are fully cycled.

Adding your Fish

Now you may begin to add your tropical fish. You will need to add fish slowly. I usually add 1-2 new fish per week. The size and the bioload of the type of fish also determines how man you can add safely per week.

Be sure to test regularly once you begin adding your new fish. The main idea is to slowly add fish so the biofilter can catch up to the new ammonia that will be produced by the new tropical fish.

If you go out and purchase 12 fish shortly after cycling an aquarium, you may cause an ammonia and nitrite spike resulting in the often-fatal “New Tank Syndrome.”

New Tank Syndrome

New Tank Syndrome is the process in which tropical fish keepers add too many fish to the tank before the process of cycling an aquarium is complete, or too many fish are added soon after the cycle.

When too many tropical fish are added at one time, the ammonia spikes, followed shortly by a nitrite spike in your tropical fish tank. There simply are not enough beneficial bacteria in the aquarium tank to breakdown the ammonia and nitrite fast enough.

The result is often fatal to your fish and unfortunately many tropical fish keepers get frustrated and get out of the hobby.

Fish Tank Cycling Tips


  • Be Patient. Success starts here.
  • Purchase a quality Freshwater Aquarium Test Kit.
  • Test your water often.
  • Change 25-30% of the tank water in extreme water conditions.
  • Start with 1-2 hardy fish such as Mollies, Guppies, or Black Skirt Tetras.
  • Raise your temperature to 80℉ to help the beneficial bacteria colonize faster.
  • Add an air stone or bubble wand. Increased oxygen will increase the beneficial bacteria colony.

Do not…

  • Rush. Patience is the key here!
  • Over feed. Feed once per day or every other day. Overfeeding will result in a longer fish tank cycle.
  • Over stock. Start off with 1-2 fish. After the aquarium cycle is complete, add 1-3 fish per week.
  • Use Ammonia removing chemical additives. Using Ammonia removing/reducing additives will delay your aquarium cycle.
  • Vacuum the aquarium gravel. Cleaning your aquarium gravel during the fish tank cycle will remove beneficial bacteria.
  • Use goldfish or feeder fish to cycle your tank. These fish are known to carry diseases and parasites. 
    Cycling an Aquarium is not as hard as you may think it is. The hardest part of cycling an aquarium is waiting. I know, you have this beautifully setup new aquarium with only 1-2 fish in there. Do not worry, successfully cycling an aquarium results in years of happiness and enjoyment with your new tropical fish tank.

 Suggested Reading:

Biological Filtration


Related posts:

One Response to “Successfully Cycling an Aquarium”

Read below or add a comment...