# anaerob proceses in the substrate



## john.shephard26 (Mar 8, 2011)

Hi I had a small debate with a friend on another forum about some processes and I'd like to hear your opinion:
I want to change some of my rocks that are embedded deep in the substrate(ADA AMAZONIA) but my friend says that I will cause a lots of disturbance with which I agree but nothing that huge amounts(50-60%) of water change wont prevent.BTW its freshly started tank(a week ago)
Here is his argue:
Deep in the soil there are anaerobic bacteria that can't breath O2 instead they breath H(!) so as a byproduct is NITROGEN SULFIDE!
Than another friend of mine joins in with:
Another compound in the soil is hydrogen sulfide which if exposed can be turned in to hydrogen sulfide and than to SULFURIC ACID!!!

PLEASE, what are your opinions?


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## TAB (Feb 7, 2009)

If its only been a week I would not worry too much, any fish/inverts? that would be my only worry, its just plants it'll be fine.

Sent from my SGH-T599N using Tapatalk


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## john.shephard26 (Mar 8, 2011)

Yes, yes, I know that, 
I'm more interested on those other "facts" that my friends were talking about...
Are those indeed facts or just their imagination?


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## Michael (Jul 20, 2010)

Your friends are frightening you with half-truths.

There are anaerobic micro-environments in virtually all aquarium substrate. These are normal, beneficial, and play an important role in nutrient cycling. Sometimes we accidentally create conditions in which large areas of the substrate become oxygen depleted. In these cases, enough anaerobic decomposition can occur to create dangerous levels of hydrogen sulfide.

This is relatively uncommon. The most common cause is substrate with too much fresh organic matter, and that is also too deep.


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## john.shephard26 (Mar 8, 2011)

Finally, Michael!I wasn't very precise, I'm a moderator at a local forum were I read this but didn't want to react since the one's who wrote this are more experienced than I'm.
It was strange for me when one of them wrote that there are hydrogen breathing(!!!) bacteria, and that by some process H2SO4 is created in a tank!I know about micro-environment, I was curious about these two facts?


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## Phil Edwards (Jan 22, 2004)

Like Michael said, you're going to get small areas of hydrogen sulfide and other byproducts of anaerobic metabolism in your substrate over time. However, in your particular substrate they're not going to be created or build up in sufficient quantity to kill anything. Typically in a granular substate like you've got those gases or byproducts diffuse toward the surface and are oxidized to a greater or lesser extent before hitting the water column. 

I once had a heavily planted tank with 5 inches of Amazonia in the back. One day I noticed a distinct line of ferric oxides about two or three inches from the top of the substrate. That was a line demarcating the oxic/aerobic from hypoxic/anaerobic zone. Anything above that was oxygenated and below that was not oxygenated. As the soluble iron species diffused upwards they hit that oxygenated layer, oxidized, and precipitated out. 

Like TAB said, go ahead and rearrange your tank as desired. 

If you're ever concerned about the build up of noxious chemicals in your substrate just give it a good siphon cleaning. That'll take care of most of the crap (literally and figuratively) sitting down in the bowels of the tank.


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## john.shephard26 (Mar 8, 2011)

Please describe for me how does ferric oxide looks in a tank, is it possible that it could build up so much in a tank that could kill cherry shrimps(a couple months ago I had a case of total shrimp genocide in my tank)?


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## Phil Edwards (Jan 22, 2004)

John, it looks just like rust, because that's what it is. No, it won't build up to toxic levels in your tank because it's insoluble in water. In fact, that rust layer in the substrate is a good protection against other harmful chemicals as they will stick to it and not get into the water column. Similar things happen around plant roots in anaerobic sediments. The iron and manganese oxide layer around the roots protects them from some nasties deep down.


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## john.shephard26 (Mar 8, 2011)

Thank You this is much appreciated.


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## Phil Edwards (Jan 22, 2004)

My pleasure. A good portion of my academic background and research is in aquatic sediments/plant substrates. I'm happy to answer any technical question as best as I can.


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