This article is sponsored by @Triquatics
Screen Shot 2019-02-26 at 9.49.04 AM.png Images are courtesy of @Triquatics. ©2019, All Rights Reserved.

The Nitrogen Cycle, as it applies to the greater natural world, is a series of chemical reactions that support all life on earth. Through these reactions, non-reactive nitrogen gas (N) and molecular nitrogen (N2) undergo a series of complex metabolic process in plants and bacteria to produce nitrates (NO3), which are usable to organisms like you and I in the production of essential proteins we rely on to develop and thrive. All behind the scenes, yet happening all around you.

But what does any of this have to do with your tank? Plenty. The Nitrogen Cycle is an ecological necessity, and all living things--including your fish--will suffer in its absence. That’s why it is crucial to take the steps necessary to create your very own, all natural, localized nitrogen cycle right in your own aquarium by starting out with an in-depth cycle. The best part? Just add ammonia!


Ammonia (NH3) in a compound comprised of nitrogen and hydrogen, and a form of nitrogenous waste--particularly in fish. While typically regarded by most as a harmful toxin (which it is, at elevated levels) due to its use in cleaning products, ammonia is a vital compound that is foundational as a precursor to plants, the foods they produce and is even implemented in the synthesis of important clinical drugs. Ammonia is, simply put, a key component to sustaining life and the single ingredient needed to jump-start your tank’s Nitrogen Cycle! Are you running a "fish-less" cycle? Get ammonium chloride here.

Screen Shot 2019-02-26 at 9.48.42 AM.png
Images are courtesy of @Triquatics. ©2019, All Rights Reserved.


If you have an aquarium with fish, it’s more than likely that the process has already begun: Since ammonia is a product of fish waste, ammonia levels will rise each and every time nature calls in your tank. Ammonia Testing is crucial to ensure levels are rising & falling as they should. Ammonia levels will also rise in the presence of uneaten foods as well as any dead and decaying organic matter. In order for this process to advance to the second phase of the Nitrogen Cycle, it is important that you simply allow the level of ammonia to rise for several days. Eventually, the water in your tank will reach toxic levels of ammonia; and while this may sound alarming and you might be tempted to clean or otherwise reduce the amount of ammonia in your tank, do not. The process will not continue on to Phase 2 until ammonia levels are high.

Due to the stressful nature of this phase (both for your fish and perhaps yourself), many aquarists have stopped using fish to cycle aquariums. Instead, these aquarists prefer to use something like a piece of raw shrimp or even fish food to "seed" the tank for the Nitrogen Cycle. Other reefers find that using some type of nitrifying bacteria supplement is what they prefer (something like Brightwell's FaStart-M). In this way, a tank can be cycled without needing to expose fish to toxic levels of ammonia.

However, if you do decide to use a live fish to cycle your aquarium, you should only use a small number (1 is sufficient) of hardy fish such as damsels. Too many fish could over-shoot the desired, albeit high, level of free ammonia and create lethal levels before Phase 2 can begin--A phenomenon known as “New Tank Syndrome.

As this first stage progresses, two types of ammonia may be produced depending on the pH and temperature of the water: Ionized ammonia (NH3+4) or unionized ammonia (NH3). Ionized ammonia is a less toxic form of ammonia and is more favorable to have in your tank during this process. Unionized ammonia, however, is able to bind to living tissue and cause ammonia poisoning even at more moderate levels. Symptoms include bottom-dwelling behaviors, inflammation and redness, and lethargy. The time required to meet the ammonia threshold is approximately 10 days, though factors such as tank size, the number, as well as the size of your fish may affect this estimation.


Once the ten days of Phase 1 have passed, a test of the water should indicate a drop in free ammonia levels. This indicates that the second stage has begun. A colony of Nitrosomonas--a chemoautotrophic bacteria--have begun to populate your aquarium. As they multiple, they oxidize the free ammonia into nitrite (NO2) which will increase by 1ppm (part per million) each day for about 15 more days as the level of free ammonia decreases.

A Nitrite Test is required to monitor that the levels have risen and are dropping. Nitrite is toxic as well; while it won’t reach the levels seen with the free ammonia in the first phase, it is more potent. Once again, should the amount of this nitrite be slowed or otherwise not allowed to reach the necessary amount for Phase 3, the Nitrogen Cycle will not continue. Continue to care for and feed your fish as prescribed, and rest assured that their good work has come into the final stretch. By (approximately) the 25th day, water testing should show a drop in nitrite from 15ppm by about 1.2ppm each day until it is gone completely.

Phase 3 is here.


The consumption of the toxic nitrite has spurred the growth of a new colony of Nitrobacter--a good bacteria that converts free ammonia and nitrite into nitrate (NO3) by using molecular oxygen (O2) in your tank’s water supply (H2O)--will be seen growing on nearly every surface of your aquarium. A Nitrate Test will be used to determine the rise and fall of nitrates. After nearly 6 rough weeks, your Nitrogen Cycle is complete and you now have an all-natural biofiltration method to remove toxic Free Ammonia from your tank! Congratulations! Your fish have worked hard to get this far. But now, with the added help of your tank’s filter to handle large, solid waste, all future free ammonia levels will be kept at a level that is virtually undetectable for the life of your aquarium.

In order to keep the number of Nitrobacters in check post-cycle, it is recommended, most of all, to continue good feeding practices to prevent an excess of waste nutrients and fish waste. Excessive free ammonia can cause a boom in Nitrobacter populations beyond what is needed in your aquarium. Additionally, introducing aquatic plants into your tank will provide additional Ammonia absorption and will replenish oxygen levels to your tank for your fish and for your Nitrobacter colonies. A simple water change will help keep Nitrobacter levels in check. If you wish to create another Nitrogen Cycle in another tank, simply collect samples of your original tank’s Nitrobacters and introduce them to your new one with no multi-week ordeal required!


Note from the Editor: This article originally appeared on the Triquatics blog, and is reprinted here with their permission.

Also, in pharmacology, "whether or not a molecule is ionized will affect its absorption, since ionic molecules are charged. Solubility favors charged species, and permeability favors neutral species." This is why there's a big difference to your livestock depending on whether the ammonia is ionized or not. The author is making the point that when you test for ammonia, you're getting a total ammonia number, but not all of that ammonia is equally hard on the livestock.

This article is sponsored by @Triquatics


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Author Profile: @Triquatics Staff Member, Adam Buesching

Adam is a writer, content creator, and reef hobbyist and is the latest addition to the Triquatics team. His ability to conduct research and fashion his findings and create interesting and knowledge-filled content for all audiences speaks for itself. When he isn’t publishing an article on tank cycling, feeding methods or another article at work, he is researching other areas of reefing.
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