Can a wet/dry filter fix nitrogen from the atmosphere?

[salty joe]

If so, it would explain the wet/dry filter's reputation as a nitrate factory...

 

[Randy Holmes-Farley Verified Community Expert]

IMO, the only organism that could fix nitrogen that is likely to grow on a wet dry is cyanobacteria. If there's no cyano visible, I think that is an unlikely contributor.

 

[Hans-Werner]

I think that "nitrate factory" has to be interpreted in a different way: A wet/dry filter rapidly oxidizes ammonium from fish excretions to form nitrate.

I agree with Randy that under normal conditions in a wet/dry filter only cyanobacteria could fix nitrogen. Other diazotrophic (reducing N2 to ammonia/ammonium) bacteria like Azotobacter are heterotrophic, needing organic carbon like sugars or alcohols. In mutualistic relationships with plants or animals like corals diazotrophic bacteria receive organic carbon from their host. In wet/dry filters this is rather unlikely to occur.

 

[Rjramos]

Wet/dry filter= aerobic bacteria which yields nitrates as end product.
Live Rock/ Deep sand bed =anaerobic bacteria yields nitrogen as end product.

 

[taricha]

I think that "nitrate factory" has to be interpreted in a different way: A wet/dry filter rapidly oxidizes ammonium from fish excretions to form nitrate.

There's a number of different reasons to favor the above explanation for "nitrate factory"
breaking N2 bond is (energy) expensive, and N is already available in the water in other forms, wet-dry filters allow a lot of flow of nutrients across biofilm under lower light condition than the tank in general - ideal for increased nitrification of ammonia to NO2/NO3.

 

[HuduVudu]

If so, it would explain the wet/dry filter's reputation as a nitrate factory...

I really don't get the nitrate factory fixation. Everything gets called that.

If you want the "real" nitrate factory then here it is: Haber-Bosch Process

 

[salty joe]

Thanks, I'm considering using a wet/dry with outside air pumped in for gas exchange. Do you see any downsides?

 

[Hans-Werner]

If you want the "real" nitrate factory then here it is: Haber-Bosch Process

Yes, but for the Haber-Bosch Process you need hydrogen which is made from gas which has got quite expensive and so have fertilizers. Cyanobacteria and bacteria do the same trick without extra gas and costs.

This is used in fertilization with the tiny Azolla water fern. Also leguminoses are known to fertilize the soil in an ecofriendly way.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks, I'm considering using a wet/dry with outside air pumped in for gas exchange. Do you see any downsides?

Only possible downside (IMO) is elevated nitrate, but if elevated nitrate is not a problem in this tank, or if you deal with some other way, it should be fine.

I doubt it will be as effective as a good skimmer though.

 

[Hans-Werner]

... leguminoses ...

You may have guessed it, I meant legumes like peanuts, lentils and beans. It seems so easy to get from the German "Leguminosen" to the English ...