Aquarium Cycling

by roshi on October 5, 2010

in Aquarium

nitrogen cycle, aquarium cycling

If your fish die again and again or your aquarium water gets cloudy, dirty or yellow then it means your aquarium needs cycling. Simply put, fish produces wastes that is toxic for fish and you have to make sure that there are enough beneficial bacteria to in the gravel to consume that fish wastes. It takes time and you can cycle your fish tank easily by following the procedure here. Click at the thumbnail above for full figure to understand the aquarium cycle.

Its called as Biological Cycle, Nitrification Process, New Tank Syndrome, Start-up Cycle or Nitrogen Cycle. It is vital for anyone planning on keeping aquarium fish to understand this process. Learning about this process will help you to be successful in keeping fish.

Nitrogen cycle is the establishment of beneficial bacteria in the aquarium (in and under gravel) and in the filter media that will help in the conversion of ammonia to nitrite and then the conversion of nitrite to nitrates. The process can take from 2 weeks to 2 months or longer to complete. The best way to monitor the nitrogen cycle is to purchase an aquarium test kit that will test for ammonia, nitrites, nitrates and ph.

Make sure that your tank is cycled. Get an API Master Test Kit and test your water for ammonia, nitrites, and nitrates. Test your aquarium water every day and write down your readings. You will first see ammonia levels rising. A few weeks or so later you should see the nitrite levels rising and the ammonia levels dropping. Finally, after a few more weeks you should see the nitrate levels rising and the nitrite levels dropping. When you no longer detect ammonia or nitrites but you can detect nitrates you can assume that it is safe to add your tropical fish.

Your readings should be 0ppm ammonia, 0ppm nitrites, and 10-20ppm nitrates.

Nitrogen Cycle Stages

Introduce Ammonia into the aquarium via fish waste and uneaten fish food. The fish waste and excess food will break down into either ionized ammonium (NH4) or un-ionized ammonia (NH3). Ammonium is not harmful to fish but ammonia is. Whether the material turns into ammonium or ammonia depends on the ph level of the water. If the ph is under 7, you will have ammonium. If the ph is 7 or higher you will have ammonia.

Soon, bacteria called nitrosomonas will develop in the aquarium and they will oxidize the ammonia in the tank, eliminating it. The byproduct of ammonia oxidation is Nitrites. We now have another toxin to deal with – Nitrites. Nitrites are toxic to fish as ammonia. If you have a test kit, you should be able to see the nitrite levels rise around the end of the first or second week.

Bacteria called nitrobacter will develop and they will convert the nitrites into nitrates. Nitrates are not as harmful to fish as ammonia or nitrites, but nitrate is still harmful in large amounts. The quickest way to rid your aquarium of nitrates is to perform partial water changes.

Monitor your tank water for high nitrate levels and perform partial water changes regularly. There are other methods to control nitrates in aquariums besides water changes. For freshwater fish tanks, live aquarium plants will use up some of the nitrates. In saltwater fish tanks, live rock and deep sand beds can have anaerobic areas where denitrifying bacteria can breakdown nitrates into harmless nitrogen gas that escapes through the water surface of the aquarium.

How to Speed Up the Cycling Process

  • Increase the temperature of aquarium water to 80°F-82°F (27°C-28°C)
  • Get some beneficial bacteria colonies by taking some gravel from an established and cycled aquarium.
  • There are products on the market that claim to introduce the beneficial bacteria. e.g. Bio-spira, Tetra SafeStart.

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