How To Cycle The Aquarium Step By Step

Greetings reader, today we are going to enter the microscopic world to explain aquarium cycling.

What is the nitrogen cycle?
What is cycling a fish tank?
How to cycle an aquarium?

Possibly we are facing one of the issues within the world of aquarium hobby that generates more debate.

Do you know what cycling an aquarium is or what cycling a fish tank is?

Aquarium cycling, also called tank maturation, is the microbiological process by which the colony of friendly bacteria settles in the tank.

The cycling of the aquarium or period of colonization of the beneficial bacterial strain in the fish tank is essential for the good health of the fish.

But let’s start at the beginning: we first explain what is the cycling of an aquarium step by step and then we see how to cycle an aquarium.

Aquarium cycling: Introduction

In an aquarium, thanks to the fish tanks and aquariums at”> accessories for fish tanks and aquariums, we are artificially recreating a natural aquatic ecosystem. And as in any biological cycle, waste is produced.

These residues come from fish waste, plants, food scraps… and will end up polluting the water, reaching toxic levels for fish life.

So why is it so important to know how to cycle an aquarium?

Fish waste and excretions release ammonia into the water column, and ammonia at certain concentrations kills fish. It’s that simple.

However, there are some «friendly» bacteria inside the fish tank filters, which transform ammonia into another element that is not so toxic for our aquatic friends.

These beneficial bacteria are part of the filtering system, and are responsible for purifying the aquarium water. Through a biochemical process they degrade polluting waste before they become toxic.

It is thanks to the beneficial bacteria that we can maintain an aquarium in healthy conditions for our fish.

This is why we favor the colonization of the aquarium by these beneficial bacteria that eliminate a large part of these dangerous residues.

This process of purification and transformation of toxic chemical elements is known as the Nitrogen Cycle, or Nitrification. You must know it in order to understand the cycling process of the aquarium.

Don’t know what the nitrogen cycle is? I’ll tell you quickly and easily.

The Nitrogen Cycle

Let’s see what this cycle of Co 2 consists of in a closed environment such as an aquarium tank, and the most important of the different stages of the nitrogen cycle.

The waste of fish, plants, and organic matter in general, when decomposed, generates ammonia-ammonium and nitrites, which are toxic compounds for fish in aquariums.

In the first of the phases of the nitrogen cycle, the nitrifying bacteria called Nitrosomonas feed on ammonia-ammonium and metabolize it, transforming it into nitrite.

That is, they convert ammonia into nitrites. But this compound is even more toxic than ammonia. It is also toxic to fish at concentrations above 0.5 mg/l.

Fortunately, another type of bacteria called nitrobacter feed on the nitr I tos that they end up converting into nitr A tos. And nitrates in low concentrations are not toxic to fish.

In short, ammonia (toxic) is converted to nitrite (toxic) and then converted to nitrate (non-toxic). And this process will only happen after the aquarium has been cycled, which is why it is so important to know how to cycle a fish tank.

Nitrates are consumed as food by plants, so putting live plants in your aquarium will help remove some of those nitrates.

And why eliminate nitrates?

Because nitrates in concentrations above 50 mg/l are also toxic.

To lower the concentration of nitrates in the water, partial water changes are made every week or two weeks.

Your aquarium, being a closed biological system, needs a bacterial colony that can take care of biological waste. Otherwise, your fish will die within a few days.

These friendly bacteria arise naturally, but in order to take care of the toxic elements, they need a period of establishment, in which they need food and oxygen.

This is where Aquarium Cycling comes in. The period of time that bacteria need to form the necessary colony and be able to take care of biological waste.

Aquarium cycling process

Now that we have covered the nitrogen cycle, let’s see how to cycle a fish tank correctly and effectively, as well as as quickly as possible.

When you already have your tank installed, and you put it to work, the natural process of cycling the aquarium begins.

Before cycling an aquarium, a suitable freshwater analysis kit must be available. Click the button below the image to see one of the best-selling aquarium water test kits.

It is necessary to have a test kit during the cycling of the tank water, to monitor the ammonia levels and to be able to detect nitrate spikes.

The Freshwater Master Test Kit is a reliable water analysis kit that many beginners and experts use in their tanks.

With these analysis kits you will know when the fish can be safely added to the tank.

Phases of aquarium cycling

1st Phase: Colonization of Nitrosomonas bacteria

Logically, for this colony of bacteria to thrive and reproduce, it needs food, that is, Ammonia.

Let’s see what three ways you have to provide food to your friendly bacteria, and then I’ll tell you which one I prefer:

1. Add fish food

The amount you should add is about 3-4 scales each day for a 100 liter aquarium. If you crumble the scales, they will decompose faster.

Continue adding fish food until the nitrite level begins to rise.

Advantages and disadvantages of adding fish food

  • We make sure not to add any toxic product.
  • This proceeding of fish tank cycling is slower, up to two more weeks.
  • We provide phosphates, which favor the growth of algae.
  • This process is less controllable.
2. Add Ammonia directly

It is very important that it is pure ammonia, without other substances such as perfumes, detergents, etc. -aquarium ammonia

Add 5 milliliters a day for every 100 liters of water, during the first 10 days of cycling.

You can do an Ammonia test to control the concentration of this substance in the water.

Between 2 and 5 mg/l is sufficient for a rapid development of the bacterial colony. Check that it does not exceed 7 mg/l.

You can also control it with the Nitrite test. After a week the level of nitrites will start to rise, and when it reaches 0.5 mg/l it will not be necessary to add more ammonia.

Advantages and disadvantages of adding Ammonia

  • It is faster and we can measure its concentration by means of a test.
  • We do not add other substances that could be counterproductive.
  • Make sure you buy pure ammonia.
3. Add hardy fish

If you have come here wondering how to cycle an aquarium with fish inside, we are not going to explain it here. If you want to know why, keep reading.

Some recommend cycling the aquarium by introducing some fish that is capable of resisting high levels of ammonia and nitrites.

But as nature lovers, we are not in favor of subjecting any fish to this “ stress ”. Especially since there are other options.

From here, for those who start in this beautiful world of aquariums, I encourage you to wait until the cycling of the water in the fish tank is complete to introduce fish.

Tips for this first stage of the aquarium cycle
  • Maintaining a temperature of 25 o C favors the reproduction of bacteria.
  • Cycling the aquarium with the light off favors the reproduction of bacteria. In addition, this will prevent the proliferation of algae.
  • Ensure a good oxygenation of the water, since the nitrifying bacteria are aerobic and need oxygen for their development.
  • Do not introduce natural plants yet, because they consume ammonia-ammonium, and will enter into direct competition with bacteria. You will prolong the cycle time.
  • The filter must be working, and it is highly recommended to use a porous material where bacteria will colonize (ceramic beads, bioballs, etc.). If it has any absorbent compound such as resins, or activated carbon, remove it during cycling.
  • Add traces of phosphate to favor the development of nitrifying bacteria.

2nd Phase: Colonization of Nitrobacter bacteria

This second stage of aquarium cycling begins when the Nitrite level begins to rise, and the ammonia level is at a minimum.

Nitrobacter bacteria will consume the nitrites generated in the first phase of the tank cycle and convert them into Nitrates.

Nitrates are food for plants, which consume them to carry out photosynthesis and oxygenate the water, thus closing the nitrogen cycle.

Tips for this second stage
  • Do not add more ammonia or fish feed when nitrites reach 0.5 mg/l.
  • You can introduce natural plants that now will help the establishment of the bacterial colony.
  • If you bring plants, you will have to connect the aquarium light 5-6 hours each day so that the plants can carry out their biological cycle. If you put more hours of light, the algae will grow quickly due to the high concentration of nitrogen. After the cycle you should gradually increase the lighting period until 10-12 hours of light.
  • You will also need to provide other nutrients for plants, such as Phosphates to reach 0.5 mg/l, and Potassium to reach 5-10 mg/l.

This second stage ends when the Nitrite level is zero. After a week continuously increasing the level of Nitrites, you will see a stabilization, and then a drop in level to zero.

The strain of nitrifying bacteria has become established in the aquarium.

3rd Phase: Nitrate Level

From now on, controlling the level of Nitrates will be one more part of the periodic maintenance of your aquarium.

The acceptable concentration of Nitrates will depend on the inhabitants of your aquarium. but genericallybetween 5-10 mg/l is a correct concentration.

Reaching 25 mg/l, you must carry out a partial change of water to lower that level. Prevents it from reaching 40 mg/l.

cycled aquarium. Aquarium cycling is over.

Cycle time of an aquarium

As a guide, it can last from 20 to 60 days, but until the levels of ammonia and nitrites are not zero, the cycle will not be finished.

There are several ways to favor the nitrogen cycle, which we will explain later. Let’s first see how to cycle the aquarium step by step and how to introduce the fish.

How to cycle an aquarium step by step

  1. 1. Assemble and prepare your tank. Place the necessary equipment in your tank and fill it with water.
  2. 2. Add a few fish food flakes or a little pure ammonia. Now, we just have to wait. Over the next few days, the scales will begin to break down and release ammonia into the water.
  3. 3. A few days later, perform the analysis to check the ammonia level in the water. We need a level of at least three parts per million (ppm). If there is not enough ammonia in the water, add more flakes or liquid ammonia and wait for it to break down before testing again.
  4. 4. Try to keep the ammonia level at about 2 ppm. Continue to test the water every other day to monitor ammonia levels. As nitrifying bacteria begin to colonize the tank, they will reduce ammonia levels by consuming ammonia. Add more fish food whenever the ammonia level drops below three ppm.
  5. 5. When bacteria consume ammonia, they begin to produce nitrites. After a week, you can start looking for nitrites, the intermediate type of chemical in the nitrate cycle. When you detect nitrites, you can tell that you have already started cycling an aquarium. You should still continue to provide ammonia as you have done so far.
  6. 6. As ammonia bacteria continue to be fed, nitrite levels will continue to rise. But there will come a time when there will be enough beneficial bacteria to convert nitrites to nitrates, the last type of chemical in the nitrogen cycle. That’s when there will be a sudden drop in nitrites and a surge in nitrates.

    When this happens, cycling is nearing completion. This can be detected by testing for nitrites, in which case a sudden drop will appear; or nitrate tests, in which case a sudden spike will appear.

  7. 7. When the ammonia and nitrite levels are close to zero, the nitrate should be stable. After about six to eight weeks have passed, ammonia and nitrite levels should no longer be detectable. At this time nitrate levels should also be stable. At this point is when you should do a partial water change and start adding fish gradually.
  8. 8. In the event that you have to add a lot of food during cycling, consider siphoning the substrate clean before adding fish. Decaying food or plant matter can become an ammonia bomb with time. If these remains are trapped in the gravel, the ammonia will not be found in the water column. But if something moves it, it could suddenly release excess ammonia.

Introduction of fish after cycling aquarium

Knowing the pH, KH and GH will allow you to know what characteristics the fish must have that you can choose for your aquarium.

You can also change the characteristics of the water to suit the species you want, but keep in mind that this will take time and money.

The process of cycling the tank usually takes six to eight weeks. And when the ammonia and nitrite levels are so low that they don’t show up in the tests, that ‘s when you can start introducing the fish.

However, do it gradually, introducing only one or two new fish at a time. Then you will have to wait a week or two before introducing more fish.

When we add a few fish at a time we keep the increase in ammonia and nitrite within the carrying capacity of the bacteria.

Every time you add new fish, you should wait at least a week to test the water again. If the ammonia and nitrite levels are low, you can add the next batch of fish.

Fast aquarium cycling

Add bacteria to the tank

And having both Nitrosomonas and Nitrobacter from the start will promote rapid aquarium cycling, because it eliminates the waiting time for nitrite to appear.

Bacteria in bottle

There used to be some fake products with the wrong species of terrestrial bacteria. When these products are used in an aquarium, it may seem at first that the tank is rapidly cycling.

But it won’t work. Because the terrestrial bacteria will drown in the water.

The result is that these products must continue to be dosed to prevent the fish tank cycling from stopping. Because of this, many people believe that these products do not work. This is a mistake.

The correct species of bacteria were identified and a way to store them in liquid form was found.

Bio-Spira was the first product with proven efficacy. And it wasn’t long before Tetra introduced the same product called Tetra SafeStart. The same product is now in even more different bottles with different names. Dr. Tim ‘s One and Only is just another example.

These bottled bacteria have been used by many successful hobbyists to rapidly cycle their aquarium. And they have been so well received because most aquarists are not patient enough.

If you decide to buy a commercial bacteria product, make sure it’s a bottle with enough for your fish tank. The larger the bottle, the more bacteria it contains.

Keep in mind that most of these products require the bottle to be shaken vigorously before use. You should also keep in mind that you have to use all the content at once, since the product expires after opening it.

Add bacteria from an established tank

It can be some gravel or some decoration, but it is best to use a piece of the filter charges.

Add filter media from a mature tank

So you no longer have to wait for bacteria to start growing naturally. The ripening process should be faster than the «natural» way.

The main source of nitrifying bacteria is the aquarium filter. Simply use filter media from an established fish tank in the new tank for a potential boost.

Add gravel from a cycled tank

Just add a handful of mature substrate on top of the new tank’s substrate to speed up aquarium cycling.

Have natural plants in the aquarium

There are certain fast-growing varieties such as Vallisneria and Hygrophila, which consume most of the ammonia. Also floating plants work well in general.

NOTE: Be careful of the risk of cross contamination.

One of the drawbacks to these techniques for speeding up tank cycling is the possibility of unintentionally transferring organisms other than friendly bacteria.

I recommend that you do not use material from a tank that is known to be contaminated with harmful organisms. Pests like snails, harmful algae and parasites like ich can ruin your fish tank.

Higher water temperature

This will encourage the multiplication of beneficial bacteria. Furthermore, the high temperature will also increase your appetite for ammonia and nitrite.

Although this won’t make a big difference in the time required for cycling, every little bit helps when you want to get your first fish in.

Higher level of dissolved oxygen

This is because Nitrosomonas and Nitrobacter bacteria require oxygen to multiply. And an oxygen-rich environment will help them reproduce faster.

In addition, it will also be necessary if the tank temperature rises as we said in the previous point. The hotter the water, the less oxygen it contains.

Final conclusions on aquarium cycling

Aquarium cycling is the most important part of setting up a new tank.

But the good thing is that it does not require any work. Just patience and regular testing of the tank water.

The colonization of bacteria in the filter will help to close the biological cycle of the fish, neutralizing their waste and making the fish tank a habitable environment.

It is essential to prevent excessive concentrations of nitrates, which we have already seen are not healthy for fish.

If the levels are too high, they will lose their color and appetite. In addition, the proliferation of algae will be favored. To prevent this, water changes should be an important part of aquarium care.

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