The process known as cycling is a way of cultivating necessary bacteria in a new aquarium. The bacteria are necessary to decompose the waste products produced by fish and other inhabitants in the aquarium. An aquarium will always need a combination of suitable bacteria cultures and frequent water changes to stay clean and provide the fish with a good environment. If you add fish to an improperly cycled aquarium they can quickly fall ill or even die, since their waste products will pollute the water. Some fish are more tolerant to moderate levels of soluble waste than others, but no fish will appreciate an aquarium with high levels of these toxic compounds.
The basic cycling method is based on gradually adding fish to the aquarium during a period of several weeks. There are several ways of jump starting this method. If you already have an aquarium, or know anyone who has, you can use this mature bacteria colony to jumpstart a new one in your new aquarium. Gravel and biological filter media is a rich source for bacteria. Keep in mind that even harmful bacteria can be included when you use gravel and filter media from another aquarium. It is therefore imperative to choose water from a healthy aquarium. Another way of jumpstarting the new bacteria colony is to buy water additives with small populations of suitable bacteria from a fish store.
A new cycling method known as ‘the fishless cycle’ has become very popular in recent years. During a fishless cycle, you do not relay on the fish to produce sufficient amounts of waste products to start up the bacteria culture. Instead, you add small amounts of ammonia to the water during the cycle. This simulates the normal cycling process since the bacteria will feed from the ammonia. Since you have no fish in the aquarium to act as guinea pigs, it will be even more important to carefully test the levels of ammonia, nitrite and nitrate.
Another cycling method is the ‘silent cycle’ where you fill the aquarium with densely planted aquatic plants. Choose plants that are sturdy and grow fast. During a silent cycle, the levels of bacteria will typically be very low and the nitrogen will instead be consumed by the plants. This is still a comparatively unusual cycling method. According to some aquarists the plants will not only efficiently cycle the aquarium, but also decrease the spikes in nitrate and ammonia levels that are often seen during the more common cycling methods.
The reason behind the necessity of proper cycling is that the balance found in a natural ecosystem need some help from the aquarist in such an enclosed place as an aquarium. It is almost impossible to arrange a perfect balance in the aquarium, and frequent water changes will therefore be necessary. The aquarists will also have to make sure that processes that would occur on their own in the wild takes place in the aquarium as well. One of these processes is cycling.
A lot of beginner aquarists start out with a small aquarium, but a large aquarium is actually much easier to keep when it comes to water chemistry. A small piece of food that is left to rotten in a small aquarium can pollute the entire environment, while a small piece of rotting food might cause just a slight change in the levels of soluble waste in a really large aquarium where there is much more water that can absorb the systemic shock.
The cycling process in the aquarium is closely linked to the so called nitrogen cycle. The nitrogen cycle is a process where waste products produced by the living creatures in the aquarium are turned into nitrate. In your aquarium, animals, fungi, and some types of bacteria will produce waste products. These waste products contain ammonia. Ammonia will also be produced when dead matter is decomposed, such as dead aquatic plants, left over food and shredded scales from fish.
These products can be converted by a type of bacteria belonging to the genus Nitrosomonas. Nitrosomonas are so called nitrifiers and will consume ammonia and excrete nitrite. Just like ammonia, nitrite is very toxic and high levels of nitrite will severely harm or even kill your fish. Fortunately, a well balanced eco-system will contain another type of bacteria – the genus Nitrospira. Nitrospira bacteria will convert nitrite into nitrate. Nitrate is not as toxic as nitrite and the inhabitants of the aquarium will tolerate nitrate better than nitrite and ammonia. This does not mean than you can allow the levels of nitrate to sky-rocket. You should always strive to keep the levels of ammonia, nitrite and nitrate low.
If you keep live plants in your aquarium, they will also help eliminating waste products since they can metabolize ammonia and nitrate. They will remove ammonia and nitrate from the water and include it in their biomass. This means that the removal will only be temporary; the plants will release the nitrogen compounds into the water again as old leaves die and become decomposed.
In an enclosed space such as an aquarium, only a part of the nitrogen cycle will take place. Nitrogen will always have to be added from outside the aquarium (which is essentially what you do when you feed your fish). In the other end of the cycle, nitrate will accumulate and must be removed by water changes. If the aquarium do not have enough bacteria to convert all the waste products into less harmful compounds, you will have to install some type of filter or perform very frequent water changes. A biological filter is a medium designed for nitrifying bacteria to colonise and thrive in. Active carbon filters can also help keeping the levels of soluble waste down, since activated carbon will absorb nitrogen as well as other toxic compounds.
As mentioned above, you can buy bacteria cultures from fish stores to jump start the cycle in your new aquarium. When you choose among different products, you should be aware of the fact that some of them might contain Nitrobacter bacteria instead of Nitrospira bacteria. Nitrobacter bacteria were earlier believed to be the main converters of nitrite into nitrate and it is true that Nitrobacter bacteria are capable of converting nitrite into nitrate. Careful studies performed in aquariums with a well established nitrogen cycle have however showed that the levels of Nitrobacter bacteria in such aquariums are close to undetectable. Nitrospira bacteria on the other hand were found in large amounts.
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