Kaix
07-27-2006, 03:15 PM
What Is the Nitrogen Cycle?
Like all living creatures, fish give off waste products (pee and poo). These nitrogenous waste products break down into ammonia (NH3), which is highly toxic to most fishes. In nature, the volume of water per fish is extremely high, and waste products become diluted to low concentrations. In aquariums, however, it can take as little as a few hours for ammonia concentrations to reach toxic levels.
How much ammonia is too much? The quick answer is: if a test kit is able to measure it, you've got too much (i.e., it's in a high enough concentrations to stress fish). Consider emergency action (water changes and zeolite clay) to reduce the danger. (A more detailed discussion of ammonia toxicity can be found later in this section.)
In aquaria-speak, the “nitrogen cycle” (more precisely, the nitrification cycle) is the biological process that converts ammonia into other, relatively harmless nitrogen compounds. Fortunately, several species of bacteria do this conversion for us. In particular, Nitrosomonas species (among others) convert ammonia (NH3) to nitrite (N02-), while Nitrobacter species (among others) convert nitrite to nitrate (NO3-). Thus, cycling the tank refers to the process of establishing bacterial colonies in the filter bed that convert ammonia -> nitrite -> nitrate.
The desired species of nitrifying bacteria are present everywhere (e.g., in the air). Therefore, once you have an ammonia source in your tank, it's only a matter of time before the desired bacteria establish a colony in your filter bed. The most common way to do this is to place one or two (emphasis on one or two) hardy and inexpensive fish in your aquarium. The fish waste contains the ammonia on which the bacteria live. Don't overfeed them! More food means more ammonia! Some suggested species include: common goldfish (for cold water tanks), zebra danios and barbs for warmer tanks, and damselfishes in marine systems. Note: Do not use “toughies” or other feeder fishes. Although cheap, they are extremely unhealthy and using them may introduce unwanted diseases to your tank.
During the cycling process, ammonia levels will go up and then suddenly plummet as the nitrite-forming bacteria take hold. Because nitrate-forming bacteria don't even begin to appear until nitrite is present in significant quantities, nitrite levels skyrocket (as the built-up ammonia is converted), continuing to rise as the continually-produced ammonia is converted to nitrite. Once the nitrate-forming bacteria take hold, nitrite levels fall, nitrate levels rise, and the tank is fully cycled.
Your tank is fully cycled once nitrates are being produced (and ammonia and nitrite levels are zero). To determine when the cycle has completed, buy appropriate test kits and measure the levels yourself, or bring water samples to your fish store and let them perform the test for you (perhaps for a small fee). The cycling process normally takes anywhere from 2-6 weeks. At temperatures below 70F, it takes even longer to cycle a tank. In comparison to other types of bacteria, nitrifying bacteria grow slowly. Under optimal conditions, it takes fully 15 hours for a colony to double in size!
It is sometimes possible to speed up the cycling time. Some common procedures for this are detailed later in this section. Warning: AVOID THE TEMPTATION TO GET MORE FISH UNTIL AFTER YOUR TANK HAS FULLY CYCLED! More fish means more ammonia production, increasing the stress on all fish and the likelihood of fish deaths. Once ammonia levels reach highly stressful or toxic levels, your tank has succumbed to “New Tank Syndrome”; the tank has not yet fully cycled, and the accumulating ammonia has concentrations lethal to your fish.
Like all living creatures, fish give off waste products (pee and poo). These nitrogenous waste products break down into ammonia (NH3), which is highly toxic to most fishes. In nature, the volume of water per fish is extremely high, and waste products become diluted to low concentrations. In aquariums, however, it can take as little as a few hours for ammonia concentrations to reach toxic levels.
How much ammonia is too much? The quick answer is: if a test kit is able to measure it, you've got too much (i.e., it's in a high enough concentrations to stress fish). Consider emergency action (water changes and zeolite clay) to reduce the danger. (A more detailed discussion of ammonia toxicity can be found later in this section.)
In aquaria-speak, the “nitrogen cycle” (more precisely, the nitrification cycle) is the biological process that converts ammonia into other, relatively harmless nitrogen compounds. Fortunately, several species of bacteria do this conversion for us. In particular, Nitrosomonas species (among others) convert ammonia (NH3) to nitrite (N02-), while Nitrobacter species (among others) convert nitrite to nitrate (NO3-). Thus, cycling the tank refers to the process of establishing bacterial colonies in the filter bed that convert ammonia -> nitrite -> nitrate.
The desired species of nitrifying bacteria are present everywhere (e.g., in the air). Therefore, once you have an ammonia source in your tank, it's only a matter of time before the desired bacteria establish a colony in your filter bed. The most common way to do this is to place one or two (emphasis on one or two) hardy and inexpensive fish in your aquarium. The fish waste contains the ammonia on which the bacteria live. Don't overfeed them! More food means more ammonia! Some suggested species include: common goldfish (for cold water tanks), zebra danios and barbs for warmer tanks, and damselfishes in marine systems. Note: Do not use “toughies” or other feeder fishes. Although cheap, they are extremely unhealthy and using them may introduce unwanted diseases to your tank.
During the cycling process, ammonia levels will go up and then suddenly plummet as the nitrite-forming bacteria take hold. Because nitrate-forming bacteria don't even begin to appear until nitrite is present in significant quantities, nitrite levels skyrocket (as the built-up ammonia is converted), continuing to rise as the continually-produced ammonia is converted to nitrite. Once the nitrate-forming bacteria take hold, nitrite levels fall, nitrate levels rise, and the tank is fully cycled.
Your tank is fully cycled once nitrates are being produced (and ammonia and nitrite levels are zero). To determine when the cycle has completed, buy appropriate test kits and measure the levels yourself, or bring water samples to your fish store and let them perform the test for you (perhaps for a small fee). The cycling process normally takes anywhere from 2-6 weeks. At temperatures below 70F, it takes even longer to cycle a tank. In comparison to other types of bacteria, nitrifying bacteria grow slowly. Under optimal conditions, it takes fully 15 hours for a colony to double in size!
It is sometimes possible to speed up the cycling time. Some common procedures for this are detailed later in this section. Warning: AVOID THE TEMPTATION TO GET MORE FISH UNTIL AFTER YOUR TANK HAS FULLY CYCLED! More fish means more ammonia production, increasing the stress on all fish and the likelihood of fish deaths. Once ammonia levels reach highly stressful or toxic levels, your tank has succumbed to “New Tank Syndrome”; the tank has not yet fully cycled, and the accumulating ammonia has concentrations lethal to your fish.