# Sulfur smell after tearing down dirted tank.



## Sarpijk (11 Jul 2019)

Hi all, so today I tore down a 50 litre tank which I had setup a year ago. I had used a layer of potting soil used for gardenias, I then used a piece of window mesh to contain the soil and sand mixed with gravel on top.
The plant was densely planted with cryptocoryne species which grew to their full potential.

After removing the fish and the stones  I revealed the soil under the mesh. I should note that plant roots had successfully grown through the mesh.Still I got this sulfur ( or was it ammonia) smell. It wasn't really unpleasant but it kinda "stuck" in my throat.

So I want to ask if this is normal or if the mesh I had used although allowed for plant roots to penetrate the soil layer still did not allow Malaysian trumpet snails to aerate the substrate properly.


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## dw1305 (12 Jul 2019)

Hi all,





Sarpijk said:


> Still I got this sulfur ( or was it ammonia) smell. It wasn't really unpleasant but it kinda "stuck" in my throat.


Almost certainly hydrogen sulphide (H2S), we can detect it really low levels (below one ppb). 





Sarpijk said:


> So I want to ask if this is normal or if the mesh I had used although allowed for plant roots to penetrate the soil layer still did not allow Malaysian trumpet snails to aerate the substrate properly.


It is normal. I think you are also right and the mesh probably contributed, by excluding MTS. 





Sarpijk said:


> The plant was densely planted with cryptocoryne species which grew to their full potential.


You will <"always get anaerobic zones"> in a fine grained substrate like soil, it isn't a problem and you don't need to worry.  You will be getting some nitrogen loss (via anaerobic denitrification) in this zone of the substrate as well, but that shouldn't matter either if the plants are growing well. I think the "_Gardenia"_ bit is probably relevant as well, because _Gardenia spp._ need an acidic pH to grow and the potting soil probably contained some organic matter, so perfect for Crypts and _Gardenia._ 

The process of H2S formation is described in the Winogradsky Column link, but the quick version is as the organic matter oxidises it will use up any initial oxygen and then diffusion (through the substrate) will be too slow to  replenish this. The organic matter then continues to decays under anaerobic (or anoxic) conditions, with the sulphate-reducing bacteria using the sulphates present (as the electron donor) and this produces hydrogen sulphide. 

cheers Darrel


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## Sarpijk (12 Jul 2019)

Thanks Darrel very helpful as always.
 I should add that yesterday I set up another 100 litre tank and again I used what had worked in the previous tank. Gardenia soil but  this time no mesh.


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## dw1305 (12 Jul 2019)

Hi all, 





Sarpijk said:


> I set up another 100 litre tank and again I used what had worked in the previous tank. Gardenia soil but this time no mesh.


I think _Gardenia_ soil should work pretty well. The UK equivalent would probably be <"Ericaceous compost">. 

There are links to using leaf mold (which would share some similarities with the _Gardenia_ potting mix) as a growing medium for <"_Cryptocoryne_ spp">.

I like low nutrients in my tanks (partly because I don't want quick plant growth) so I use approx. 90% sand - 5% leaf mold - 5% clay as a substrate. All the clay is alkaline around Bath, so I go out to the <"greensand to the east of us"> to collect it. 

cheers Darrel


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## Sarpijk (12 Jul 2019)

I too like slower plant growth that is why I have opted for Cryptocoryne sp.and a low tech approach. I used soil sprinkled with some osmocote and added laterite balls I had around. Should work well I never had Wendii Crypts reaching 40 cm.


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## Sarpijk (19 Dec 2019)

dw1305 said:


> Hi all,Almost certainly hydrogen sulphide (H2S), we can detect it really low levels (below one ppb). It is normal. I think you are also right and the mesh probably contributed, by excluding MTS. You will <"always get anaerobic zones"> in a fine grained substrate like soil, it isn't a problem and you don't need to worry.  You will be getting some nitrogen loss (via anaerobic denitrification) in this zone of the substrate as well, but that shouldn't matter either if the plants are growing well. I think the "_Gardenia"_ bit is probably relevant as well, because _Gardenia spp._ need an acidic pH to grow and the potting soil probably contained some organic matter, so perfect for Crypts and _Gardenia._
> 
> The process of H2S formation is described in the Winogradsky Column link, but the quick version is as the organic matter oxidises it will use up any initial oxygen and then diffusion (through the substrate) will be too slow to  replenish this. The organic matter then continues to decays under anaerobic (or anoxic) conditions, with the sulphate-reducing bacteria using the sulphates present (as the electron donor) and this produces hydrogen sulphide.
> 
> cheers Darrel


Hi Darrel was just reading again this older post and I noticed your reference to anaerobic territories when using soil. Does that mean that the Laterite balls I have used when setting the tank can be utilised by plant roots for Fe absorption?


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## dw1305 (19 Dec 2019)

Hi all,





Sarpijk said:


> Hi Darrel was just reading again this older post and I noticed your reference to anaerobic territories when using soil. Does that mean that the Laterite balls I have used when setting the tank can be utilised by plant roots for Fe absorption?


I’m not sure, it would depend on what proportion of the iron is in compounds that could become reduced in anaerobic conditions.

I’m going to work on theory that some oxides and hydroxides will be reduced, and that iron ions will become available.

Cheers Darrel


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