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Nitrogen Cycle

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How many fish can my aquarium support? How much food do my fish require? Why did my fish die? Many times these questions can be answered through an understanding of water chemistry and, in particular, how nitrogen appears in a system. In this module you'll use a virtual aquarium to study the nitrogen cycle. You will investigate how nitrogen moves in its various forms through an aquatic environment. Some types of nitrogen are helpful to organisms, while other kinds can be deadly. Your challenge is to keep the fish in your aquarium alive for as long as possible. Ready? Bait your hook and let's go fishing!

Nitrogen Cycle Brochure

Nitrogen Cycle Brochure

What is the nitrogen cycle?

The nitrogen cycle is also known as the biological cycle or the nitrification process, and is a part of every aquarium. This process allows for the production and establishment of beneficial bacteria in the aquarium and in the filter media. The bacteria helps in the conversion of ammonia to nitrite, then nitrite to nitrate. This process can take anywhere from two weeks to two months to complete. It is very important for anyone planning on keeping aquarium fish to understand how this process works.

What is nitrogen?

Nitrogen is a nonmetal chemical element represented by the symbol "N" on the periodic table. Elemental nitrogen is a colorless, odorless and tasteless gas that occurs in all living organisms. Nitrogen is created by fusion processes in stars and is estimated to be the seventh most abundant chemical element by mass in the universe.

Why is nitrogen important?

Nitrogen is the largest single component of the Earth's atmosphere, accounting for about 78% by volume of dry air. Nitrogen is also a major component of amino acids, proteins, nucleic acids, and most neurotransmitters. It is a large component of animal waste, in the form of urea, uric acid and ammonia.

What is the difference between ammonia and ammonium?

Ammonia (NH3) is electrically neutral, while ammonium is a positively charged ion (NH4+). Ammonium is the form of nitrogen that aquatic plants can absorb and incorporate into proteins, amino acids, and other molecules. Ammonium is a waste product of metabolism in animals, and high concentrations can enhance the growth of algae and aquatic plants. Bacteria can also convert ammonium to nitrate (NO3-), which lowers dissolved oxygen. Ammonia, on the other hand, is commonly used as fertilizer and general purpose household cleaner. Household ammonia (ammonium hydroxide) is a solution of NH3 in water and is used to clean glass, porcelain and stainless steel.

What is Nitrosomonas?

Nitrosomonas is a genus of rod shaped bacteria that are chemoautotrophs, which means they synthesize the nutrients they need from molecules in the environment. These rare bacteria are utilized in the biological filter to convert ammonia into less toxic substances such as nitrites. They are very useful in the treatment of industrial and sewage waste.

What is a nitrite?

Nitrite (NO2-) is a food source for live plants. Nitrite is a chemical preservative used in cured meats like pepperoni, hot dogs, ham, sausage, and deli-styled meats, as well as other processed foods. They are known to dilate blood vessels, which can cause headaches in some people. Nitrite is converted from free ammonia and is harmful at high levels.

What is a nitrate?

Nitrate (NO3-) is naturally present in soil, water and food. In the nitrogen cycle, bacteria convert nitrogen to nitrate, which is taken up by plants and incorporated into tissues. Animals that eat plants use the nitrate to produce proteins, and the nitrate is later returned to the environment in their feces. After bacteria convert (reduce) nitrate to nitrite in the environment, the nitrogen cycle is completed when they convert the nitrite to nitrogen. Nitrates are primarily used to make fertilizer, glass and explosives, and are much less toxic than nitrite.

What does Space Factor mean?

Have you ever been crammed into a small elevator with a large number of people? How did that make you feel? Just as people need a certain amount of empty space to feel comfortable, fish also have minimum space requirements. Some fish cluster in schools and need less space, while other fish must have lots of room for moving. In the Aquarium Simulation, the fish tank holds 140 liters when full. A Space Factor value of 10 is assigned when no fish are in the full tank. As more fish are added to the tank, the Space Factor value decreases. For example, adding two koi drops the Space Factor reading to 3.5, which indicates the tank is becoming crowded with fish.
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