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How to cycle your fish tank quickly

Before adding any fish and/or aquatic life to your fish tank, it is essential that you build up beneficial bacteria in your aquarium. Without doing so, your fish will quickly die off.

This guide at Aquarium Blueprints will help you “cycle” your fish tank with beneficial bacteria.

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What is the Nitrogen Cycle?

Before we begin, let’s first educate ourselves about the Nitrogen Cycle. All of the organic wastes (uneaten fish food, fish poop, fish urine, dying plant matter, dead fish, etc.) will result in ammonia, a compound that is highly toxic to fishes.

Fortunately, there is a bacteria called Nitrosomonas, which converts ammonia into nitrite. Although not as toxic as ammonia, nitrite is still very harmful when exposed to fish.

Thankfully, there is another bacteria called Nitrobacter, which coverts nitrite to nitrate. Nitrate is a lot less harmful when compared to ammonia and nitrite. With that said, prolong exposure to high concentration nitrate will lead to long term health problems for your fish.

The Nitrogen Cycle is when ammonia is converted to nitrite and then nitrite is converted to nitrate. To have a fully cycled aquarium, your water should have no traces of ammonia and nitrite. For nitrate, the generally accepted safe amount to have in your aquarium is up to 40 parts per million (ppm). If you have more sensitive fish and/or planning to breed fish, then it may be better to keep nitrate to below 20 ppm. If you fish to grow plants in your aquarium, you should keep nitrate to above 5 ppm or you might risk starving your plants.

How long does it take to completely cycle a fish tank?

For a tank to be completely cycled, it will usually take at least 6 to 8 weeks. This is assuming that you are constantly adding enough ammonia to your aquarium for the Nitrosomonas and Nitrobacter bacteria to be kept alive and reproduce.

The only way to truly know that your fish tank is fully cycled is to test your water parameters. After 24 hours of adding your ammonia to your tank water, use a test kit. If there are no traces of ammonia and nitrite, then you should be ready to begin adding fish to your tank water as long as your nitrate levels are safe (below he aforementioned 40 ppm concentration level).

How to add surface area to cycle your aquarium

Before you being cycling your fish tank, we recommend adding a lot of surface area for the beneficial bacteria to grow.  The more surface area you have, the more Nitrosomonas and Nitrobacter will be grown assuming that there are also plenty of ammonia present during the cycling process as well. By having a large beneficial bacteria community, you will be able to keep more fish.

To add more surface area to your tank, we recommend using a substrate that fill your fish tank to at least two inches deep. If you don’t have a filter yet, we highly suggest getting one that is designed for the size of your aquarium (you can check out our fish tank filter guide for more details). If you are planning to add rocks and/or decorations to your tank, then you should do it before starting the nitrogen cycle. All of the above add surface area for beneficial bacteria to grow.

What you should use as a ammonia source when fish tank cycling

In order to grow beneficial bacteria, you first need an ammonia source. There are several sources you could use when cycling your aquarium.

What is Fish-In Cycling?

The first method of cycling is live fish. The most commonly used fish for cycling a freshwater tank is either Zebra Danios or White Cloud Minnows. We don’t really recommend using fish as an ammonia source as the cycling process can be cruel to the fish.

Instead of live fish, you might want to used dead aquatic life. The most common “dead fish” method is by using a raw shrimp that you can buy from the supermarket. The rotting shrimp will produce ammonia to help grow the Nitrosomonas and Nitrobacter bacteria. There are a few issues with this method, however, as the shrimp you cloud your water and can also give your tank an unpleasant smell.

What is Fish-less Cycling?

The fish-less method, in our opinion, is the best for cycling your fish tank. You can simply use a pure ammonium chloride solution (we have great success using Dr Tim’s Aquatics Ammonium Chloride, which you can check out our full review here). With this method you don’t have to wait for organic matter to decompose and turn into ammonia. Not to mention that it is easier to keep track of the ammonia level in your water column.

You can also add ammonia to your water through fish food. Rotting fish food will produce ammonia that will kick start the cycle.

What aquarium tools do you need for the cycling process?

As we already stated above, we highly recommend adding a filter as well as substrate (with a depth of at least 2 inches), to your tank before you begin the nitrogen cycle. Doing so will add a lot of surface area for your beneficial bacteria to grow. Not to mention that your filter will also help add oxygen to your tank water, which is also needed by the bacteria, as it agitates the water surface and causes gas exchange to occur.

If you are using tap water for your fish tank, then we highly recommend getting an aquarium water conditioner. The conditioner will remove chlorine and chloramines, both of which are toxic to your Nitrosomonas and Nitrobacter colonies. It will also detoxify any heavy metals from your tap water. For a conditioner, we recommend getting Seachem Prime (you can find our review for the product here).

One last essential equipment you need is a test kit. As we already stated, your tank is considered to be full cycled when there are 0 ppm of ammonia, 0 ppm of nitrite and some traces of nitrate. The only way to know how healthy your water parameters are is by testing a sample. We use API Master Test Kit, which you can find out more information in our review.

How to speed up the tank cycling process

As we already stated above, the cycling process can take at least 6 to 8 weeks to complete. Fortunately, there are several ways to significantly speed up the process.

The first is by adding beneficial bacteria to your tank. You can do this by using substrate, filter media or decorations from already established aquariums. What we don’t recommend using is the tank water from an existing fish tank as the beneficial bacteria mainly attaches themselves to surfaces and, thus aren’t free floating most of the time.

There are also commercial products available that will add the beneficial bacteria to your water. Please keep in mind that, although some of these are advertised to instantly cycle a tank, we still highly recommend doing a test to make absolutely sure that the cycle is properly functioning before you start adding fish.

Another way to speed up the process is by using a heater to increase the temperature anywhere from 80 to 87 degrees Fahrenheit (or 27 to 30 Celsius). Increasing the heat will force the Nitrosomonas and Nitrobacter bacteria to grow and reproduce faster when compared to colder temperatures. Just make sure to adjust the temperature again, after your tank is fully cycled, to fit the needs of the fish species you are planning to add to your tank.

We also recommend using crushed corals. Your tank water will naturally become more acidic over time due to the organic wastes. Tank water with lower pH (below 7) will inhibit the growth of your beneficial bacteria. Crushed corals are designed to leach traced compounds when the water gets too acidic; as a result, your pH will be raised and stabilized. You can either add crushed corals as a substrate, place them in your filter or add them to a filter bag and then put them into your aquarium.

Last but not least, we recommend using live plants. Like the beneficial bacteria, aquarium plants will also consume ammonia. As an added bonus, plants will also consume nitrate; as a result, you won’t have to perform a water change as frequently and substantially when compared to a plant-free fish tank. While there are many aquarium plants available, we recommend getting ones that are beginner friendly, don’t require a high lighting fixture and won’t die off easily (i.e. Hornworth, Java Fern and Java Moss).

How to cycle your new fish tank as fast as possible

If you want to cycle your aquarium as fast as possible then we recommend first setting up your tank with a filter, heater, plants (we recommend Java Moss as it doesn’t require a lot of light and is considered to be extremely hardy), decorations as well as a substrate bed of at least 2 inches in depth. Once you have everything set up, take the following steps.

  1. Add water to your tank. You should use a water conditioner to make the liquid suitable for beneficial bacteria. As we previously stated, the conditioner we used is Seachem Prime, which is available on Amazon. (#CommissionsEarned). Turn on the heater and set it to a range of 80 to 85 degrees to promote faster reproduction.
  1. Add an ammonia source. We recommend using Dr Tim’s Aquatics Ammonium Chloride (which you can find on Amazon with this link) (#CommissionsEarned) so that you will know a more accurate idea in terms of the amount of ammonia you are adding to the water column. Follow the instructions printed on the package of the bottle in order to achieve 2 ppm of ammonia. Although you can add more, we don’t recommend it as getting the ammonia concentration of 5 ppm will hinder your fish tank cycle. 2 ppm should give you a good amount of ammonia source to start while also giving you plenty of margin for error in case you accidentally overdosed.
  1. Add beneficial bacteria. You have several options here. You can try taking filter media, substrate and decorations from an already fully cycled fish tank. If you have no access to an established aquarium, then you can also buy a commercially available beneficial bacteria additive. If you are interested in getting one, then we recommend taking a look at Seachem Stability Fish Tank Stabilizer, which you can find on Amazon.(#CommissionsEarned).
  1. Test your water for ammonia. If you are looking for a test kit, we recommend using the API Master Test Kit, which you can find on Amazon with this link. (#CommissionsEarned). Follow the instructions carefully when testing for ammonia and the keep an ongoing log of the measurements. Make sure to test your water for ammonia daily during the cycling process.
  1. Once you notice that your ammonia levels are decreasing in your tank water, start testing your water for nitrite. Follow the instructions carefully when testing for nitrite. Test for the compound daily, along with ammonia, and keep an ongoing log for both.
  1. If your ammonia level in your aquarium water reaches 0 ppm before your nitrite levels reaches 0 ppm, then you should add more ammonia. This is because you risk starving, and eventually killing, the Nitrosomonas bacteria if there aren’t any traces of ammonia in the water column. We recommend dosing just enough ammonia to achieve a ppm of 0.5 (if you are using the Dr Tim’s Aquatics Ammonium Chloride, then this means adding 1 drop per gallon in your tank water).
  1. Continue testing your fish tank water for ammonia and nitrite. Keep adding ammonia to the tank if you noticed that the ammonia ppm reaches 0 while there are still traces of nitrite still present in the water column. Your ultimate goal is to get both the ammonia and nitrite levels to 0.
  1. Once you managed to get 0 ppm ammonia and 0 ppm nitrite, it is time to test for nitrate. Unlike the other two compounds, most fish species can tolerate some nitrate in the water column. With that said, a concentration of nitrates of more than 40 ppm can harm the aquatic life in your tank over time. So follow the instructions carefully when testing for nitrate. If it is over 40 ppm, then you should do a water change (don’t forget to add water conditioner or you will risk killing the beneficial bacteria) to bring the levels down to a safer level.
  1. Once the tests show that you have 0 ppm of ammonia, 0 ppm of nitrite and less than 40 ppm of nitrate, then you tank is technically considered to be fully cycled and you can begin adding fish. We highly recommend adding a small amount of fishes, in relation to the size of your tank, in the beginning to prevent ammonia and/or nitrite spikes that could kill your newly added fish.
  1. After adding your new fishes, continue to test your water daily for ammonia, nitrite and nitrate levels. If you notice traces of ammonia and nitrite, then you should do a water change, in order to bring down the toxic levels to as low as possible. You should also do a water change if your nitrate level gets above 40 ppm.
  1. If you notice that the newly added fishes aren’t resulting any spikes to ammonia and/or nitrite after a week of testing, then you can add a few more fish to your tank and then repeat the same process as the previous step.

Every time you add new fish, make sure to test your water daily for a week to make sure you aren’t overstocking your tank and, therefore, overloading your beneficial bacteria. Even if you aren’t adding new fish, we recommend testing your water weekly and then doing the appropriate amount of water change to keep your water pristine for your aquatic life.