The Nitrogen Cycle

In a closed environment, such as your aquarium, many things such as fish waste, excess food, decaying plant matter (if you have live plants) will build up toxins inside of the water. Since there is no big water to dilute such factors, we must make sure that we create and have a stable biological filtration to break down toxins happening at all times. There are three common stages to this biological filtration, in which different types of beneficial bacteria eat only a specific type of toxin that is created naturally. Ammonia (NH3) is the first toxin that is created, and is one of the most highly toxic ones throughout the stages. Slowly beneficial bacteria will build up and break down this ammonia into nitrite (NO2) which is less toxic. Once again, the beneficial bacteria that breakdown nitrite slowly build up to turn this into nitrate (NO3). Although nitrate is less toxic than the previous three, at high concentrations is can be fatal to most inhabitants inside of your aquarium. Live plants will help out by absorbing all three of the toxins in the previous stages, and release oxygen back into the water during the day. Please also make sure to always use a water dechlorinator when doing water changes, since any amount of chlorine will kill off any beneficial bacteria.

Now, we cannot just buy these beneficial bacteria as they must be seeded onto your filter media on their own. If they are exposed to air at all, they will slowly die off even if it's just for a few minutes. Therefore, we must find a way to build up ammonia so that the bacteria can build up on their own with our equipment. This is called cycling, and there are two methods so do this that each have their own positives and negatives associated with doing them. Please be aware that cycling an aquarium can take anywhere from a minimum of 3 weeks upwards to months at a time depending on how much filter media your aquarium has, what method you are using, and the concentration of such bacteria in your air.

FreshAquaria highly recommends the API Freshwater Master Test Kit during both cycling methods, as test strips are highly inaccurate and can cause false positives or false negatives.

Fishless Cycling

This method of cycling involves adding no fish or invertebrates inside of the aquarium during, and is by far the most safest and easiest method. By not having any inhabitants inside of the aquarium, you are allowing for all of the correct amount of beneficial bacteria to grow at a rate where you can fully stock your aquarium once you are done. There are some heavy negatives toward this method, as you will be unable to stock your aquarium with any fish or invertebrates during this time.

Steps & Maintenance

  1. Add in your selected source of ammonia (can be a dead fish, dead invertebrate, pure ammonia bottle, fish food, etc.) to raise the level up to 4PPM. Do not turn on your setup's lights at any point since algae will form as we are creating perfect conditions for it.
  2. Start testing once a week for ammonia to start to decline, it might take only a few days and sometimes it can take up to a few weeks. When you see ammonia start to decline then you know that your cycle has started, and to get ready for the concentrations to rise quickly and then fall slowly. Once the readings show any ammonia below or at 1PPM then you know it's time to add in more ammonia from your source to bring it back up to 4PPM.
  3. Start testing for ammonia and nitrite twice a week, you'll slowly start to see that ammonia is falling quickly and that nitrites are starting to rise. Once the readings show any ammonia below or at 1PPM then you know it's time to add in more ammonia from your source to bring it back up to 4PPM. If the readings start to slow nitrites slowly falling then you want to test for nitrates.
  4. Start testing for ammonia, nitrite, and nitrates every other day. At this point, we want to make sure that ammonia can get turned into nitrite, and then nitrate within a day or two. If you ever get to the point where they are off the charts, feel free to do a 50-60% water change.
  5. If it can turn your ammonia source into nitrites, and then nitrates within a day or two then your aetup is now fully cycled, and ready for it's inhabitants. Congratulations!

Fish-in Cycling

This method of cycling involves adding some hardy fish or invertebrates inside of the setup during the whole cycle, and is by far the method to use if you want your setup to not look empty for weeks. There are some very heavy negatives toward this method, since you will need to always be on top of the water parameters every day (as if the various toxin levels get above 0.25PPM then you need to do a water change). Another negative is that during this method, you are putting heavy stress under any fish and/or invertebrates that you keep inside. A common sign is red gills, lacking of an appetite, staying in one place, or trying to jump outside of the setup if at all possible. These can all be reduced if you stay on top of the water changes and make sure to do all of the tests required for each step.

Steps & Maintenance

  1. Add in your selected hardy fish and/or invertebrates, making sure that they are a known hardy species as anything delicate will most likely die during this method.
  2. Start testing every other day for ammonia to show up, it might take only a day and sometimes it can take up to a few weeks. When you see ammonia you know that your cycle has started, and to get ready for the concentrations to rise quickly and then fall slowly. Once the readings show any ammonia above or at 0.25PPM then you know it's time for a 25-50% water change.
  3. Start testing for ammonia and nitrite every other day, you'll slowly start to see that ammonia isn't building up as quickly as before and that nitrites are starting to rise. Continue doing the tests and water changes for ammonia, as it will not harm then nitrite stage. Once the readings show any nitrite above 0.25PPM then you know it's time for a 25-50% water change.
  4. Start testing for ammonia, nitrite, and nitrates every other day. You'll slowly start to see that ammonia should be near or under control by the beneficial bacteria now, nitrites shouldn't be building up as quickly as before and that nitrates are starting to rise. Continue doing the tests and water changes for ammonia and nitrite, as it will not harm then nitrate stage. Now you will being doing a weekly water change of 20% for the lifetime that you have the setup since you must manually lower the nitrates as there is not any beneficial bacteria that breaks this toxin down.
  5. If it can turn your ammonia into nitrites, and then nitrates within a day or two then your aquarium is now fully cycled, and ready for it's inhabitants. Congratulations!

Pond and Live Plants Cycling

This method involves the fact of over planting using freshwater plants so that they can soak up any of the toxins and allow for you to have fish right away. This method is one of the most common used in planted aquariums, and is the reason why ponds are able to be setup in a matter of days stocked fully without any real cycling required. There are some negatives to this, which include the fact that you must know what types of plants you want inside of your setup, you must know how to take full care of them so that they do not die and cause even more toxins to be in the water, and that you still will have to do water checks however not as frequently as the above methods.

Steps & Maintenance

Starting Bacteria Products

There are many various products that claim to create an established cycle in your setup within a matter of days. Sadly, most if not all of these products do not create nor help an established cycle but instead prolong the timeframe required to stabilize a cycle. A handful of these products will contain traces of decaying matter, in which ammonia will be added into the water (at a very dilute form) to kick start it faster, however there is no way for them to package any of the beneficial bacteria as they need a constant water flow. Many questions arise when they want to know, is it worth buying and/or using, how fast does this speed up my cycle, and what are the possible risks from using it. Since there is no real proof that they work and many examples of how they do not, we still recommend that any owner using such products do so under a close eye.