Basic Water Chemistry
The Nitrogen Cycle
by MARCichlids
Establishing and controlling the nitrogen cycle is the most important and fundamental principal for maintaining life in a closed aquatic system, or aquarium. A beginning aquarist should fully understand what the nitrogen cycle is and how it works before attempting to set up an aquarium.
When starting a new aquarium, it is most important to establish a good bacteria culture of nitrifying bacteria for the nitrification process to function. This is accomplished by introducing fishes and plants in a freshwater aquarium, or fishes, invertebrates, and / or live rock in a reef aquarium. Bacteria cultures are available from several manufacturers, but the bacteria will be introduced with any living organisms put into the aquarium. These bacteria require a source of oxygen, as well as a large amount of surface area in the aquarium to thrive. They will live on any and all surfaces in the tank. Filters, such as undergravel or wet/dry filters also provide surfaces for nitrifying bacteria. Various filters media are also available to provide surface area for bacteria in canisters filters, power filters, and internal filters. Filters and filter media are limited in the number of bacteria they can support, limiting the amount of fishes that can safely be kept in the aquarium. Testing the water, as well as limiting the fish population, are extremely important.
Fishes' wastes, excess food, and other decaying organic material decompose, or break down, yielding a toxic chemical called ammonia (NH3). Even in low levels, ammonia will increase the breathing rate of fishes by irritating gill tissues. Ammonia is more quickly absorbed by the blood than oxygen is. When the fishes' blood absorbs oxygen, as it is supposed to, it binds with oxygen carrying red blood cells to form hemoglobin, just as a human's blood does. Damage to the body tissues of both fishes and invertebrates will follow, causing disease and death.
Aerobic bacteria, or bacteria that require oxygen to live, called Nitrosomonas, convert ammonia into nitrites. Nitrite is as toxic to fishes as ammonia is, by destroying the hemoglobin in the blood of fishes and invertebrates. Without hemoglobin the blood cannot carry oxygen, and this will also cause disease and death.
However, the nitrites are again converted by a second bacteria, called Nitrobacter, into nitrates, which are a far less toxic compound than either ammonia or nitrites. However nitrate levels can cause stress, encouraging disease, as well as stunt fishes' growth. Regular use of chemical test kits to monitor water quality in the aquarium is highly recommended.
Nitrate removal can be accomplished by several means. Small amounts of nitrates are absorbed naturally by plants and algae. The remainder can be removed by a good aquarium maintenance program. Regular partial water changes, cleaning filter cartridges, vacuuming substrates and gravel, removing detritus (organic wastes buildups) will solve most nitrate problems. Nitrate removing filter media, as well as denitrators and protein skimmers may also be needed. Denitrators will biologically remove nitrates while protein skimmers will remove organic wastes before the Nitrogen Cycle breaks them down into nitrates.
|
