# Question about carbon source for bacteria in gravel



## Harry Muscle (Oct 17, 2007)

According to Tom's Non CO2 Method article (http://www.barrreport.com/showthread...on-CO2-methods), using mineralized soil, peat, or leonardite under the gravel provides a source of carbon for the bacteria living in the gravel which in turn allows the bacteria to use up oxygen in the gravel, thus allowing better transfer of nutrients to the roots (hope I understood that right  ).

The question I have is what happens when the carbon source runs out? Does anything else in the tank eventually start to supply the bacteria with carbon? For example does all the "crap" that accumulates eventually in the gravel take over this role of being a carbon donor?

Thanks,
Harry


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## El Exorcisto (Aug 10, 2006)

You can't supply enough crap to keep it going indefinitely. The good news, it'll take a couple years to expend soil's goodies.


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## Diana K (Dec 20, 2007)

It will be replenished as the waste (fish food, poop, dead leaves) falls and decomposes.


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## Phil Edwards (Jan 22, 2004)

Harry,

Truth be told, you want oxygen in as much of your substrate as possible. Plants' roots require oxygen for respiration and oxic conditions allow for good root development as well as better nutrient retention in the substrate. What happens when your substrate goes anoxic is Iron and Magnesium + Phosphate complexes break down, releasing ions of those species into the substrate water. That's generally a good thing, but can cause problems of their own if it's occurring too much. As soon as the dissociated ions dissipate through the substrate and hit an oxic patch the Iron and Magnesium will oxidize and recombine with Phosphorus. 

Common sources of carbon for aquarium substrates include feces, decaying food and plant matter, organic compounds exuded by plant roots, CO2 gas "exhaled" by plant roots, and natural dissociation of any carbonate species in the substrate minerals. You're all set for sources right there. 

The short of it is, don't worry about supplimenting Carbon in your substrate solely to culture more bacteria. In the grand scheme it's better to let the substrate ecosystem and nutrient fluxes develop on their own. Anything we do to disturb that may create a situation that's undesireable or at the very least, unsustainable without continued future disturbance/supplimentation.

Cheers,
Phil


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