The nitrogen cycle of an marine aquarium (it is essentially the same in freshwater aquariums) is a chain reaction in nature resulting in the birth of various types of nitrifying bacteria, each with their own job to do. Each new bacteria born consumes the previous one, and in turn gives birth to the next bacteria.
The three components involved to make this happen are ammonia (NH³ or NH³+4), nitrite (NO²), and nitrate (NO³). In general the nitrogen cycling process usually takes about 30 days, but there is no exact time frame for this process to complete its task, as each aquarium is different. Factors such as how many fish, other livestock, and organic matter is present in the tank can vary the completion time, one way or the other. Testing your aquarium water during cycling is very important, as this will tell you what phase the aquarium is in at any given time throughout the process.
To accomplish the biological or nitrogen cycling process, ammonia is required to kick start the whole thing, and this is usually introduced into the aquarium by adding a few fish. Ammonia is produced in many ways. It not only comes from the waste of live fish, but all other marine animals and organisms as well as dead or decaying matter, which includes plants. Why do you think it is so important to remove excess uneaten fish foods, dead animals, or decomposing plant matter from an aquarium as soon as possible? They are contributors to a rise in unwanted ammonia in aquariums. Also, why is it important to not overfeed your fish, especially during the cycling period? More food = more waste = more ammonia!
Now during the cycling process certain bacteria convert ammonia into nitrite, and at various stages both of these elements build to highly toxic levels, which endangers the lives of the animals. Do you see the catch 22 here? If fish are needed as the source of ammonia to start the cycle, and during the process the ammonia and nitrites reach toxic levels that put them in harms way, which many aquarists do not want to do, how can you cycle the tank "without" the fish?
Tank Cycling Options Without Using Fish
- Add some hermit and/or true crabs instead. They are pretty hardy animals, rather inexpensive, and will cycle your tank just as well as fish do. Besides, they can be pretty entertaining critters to have. Just feed the hermit crabs and true crabs either flake, pellet or frozen fish foods and they will do the rest, starting to produce the ammonia you need to feed the bacteria.
- Cycle the tank with live rock and/or live sand. These are both living parts of the reef that produce waste. Not only will they cycle the aquarium, they become the main source of biological filtration itself. When you use live rock or live sand that has come from a cycled tank, they already have both of the live bacteria (nitrosoma and nitrobacter) you will need to complete the cycle. There won't be a huge population of these bacteria, so make sure to add live critters to your tank slowly until the bacteria population has a chance to spread to the rest of the tank.
- Add ammonium chloride. Read John Tullock's " Cycling the Tank" article, or refer to Martin A. Moe, Jr.'s "The Marine Aquarium Handbook: Beginner to Breeder" ( read review & compare prices) for step-by-step instructions on how to use this cycling method.
- Use the Cocktail Shrimp Cycling Method which involves putting a few cocktail shrimp in the tank and letting them decompose, creating ammonia in the process. Once the shrimp have produced enough ammonia to start your cycle and the cycle has completed (nitrate present and nitrites reduced to zero) remove what is left of the shrimp and start slowly adding your livestock to the tank.
- Cocktail Shrimp Cycling Discussion
- This may sound a little off the wall, and people have done it, but you can use human urine as the ammonia source.
Did you know there are ways to speed up the nitrogen cycling process rather than having to wait around for nature to run its course?