Not your typical nitrogen cycle question

[fish wrangler]

I'm taking an environmental biology class in college and am looking at that for my major. The professor discussed the nitrogen cycle, that se all know, but at the end of the nitrogen cycle the nitrates are turned back into nitrogen gas and released into the atmosphere.
If this is the full nitrogen cycle then why isn't it happening in our tanks? Or is it happening and I'm just not seeing it?

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[jarrod0987]

It can if we design it in. Those bacteria are not as efficient so you need a lot of surface area in an anoxic environment. Such as a deep sand bed. Also....It turns out adding in organic carbon really made a big difference. It is a big discovery in the hobby in the last 8 years or so but it is debated weather it is true denitrification or just the bacteria doubling like crazy which is not the same. I would listen to the professor before I listened to a hobbyist Although some of them probably do have degrees in this area I don't think most do.

 

[nkoyko]

Jarrod is correct on the anoxic part. To complete the entire nitrogen cycle you would need anaerobic (no oxygen) bacteria to complete it. I'm not certain if a deep substrate would be enough of an anoxic environment for that to occur. In your fish tank is an aerobic (oxygen) environment which is why the oxic part of the cycle is able to occur.

 

[jarrod0987]

People also use products made for this like Seachems Matrix or De Nitrate. Also you can use Pumice or Pumice blocks etc. Deep gravel won't work. You need sand. Miracle mud also works. They have a fresh water version but the system is expensive.