# gas bubbles coming up from the substrate



## helenf (Mar 24, 2008)

In my 10 gallon "el natural", which has been running for about 2 or 3 months now, I have noticed something that disturbs me (other than the persistent nitrite levels - see my other thread for that). 

When I lightly vacuum the gravel, barely touching the end of the vaccum to the gravel and certainly not disturbing the soil underneath, I see bubbles of gas escaping from the substrate. The effect is like seeing air bubbles come out of a sponge squeezed underwater, if that makes sense. 

What gas is this?

Is this bad? Is it very bad? 

The effect seems to happen mostly in the area that is unplanted (which is roughly a semicircle with a 15cm (6 inch) radius). The rest of the tank is heavily planted, but I leave this area for viewing the fish better and so the corys have a good place to hunt for food. 

The substrate is 1.5 inches of potting soil and 1 inch of gravel. The plants are mostly fast growers, mostly hygro and similar, and are growing well. 

I don't know if I need to worry about this gas or not. Any suggestions would be welcome.


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## rohape (Feb 7, 2005)

I wouldn't worry about the gas. For the most part it's normal. It's only in the middle because the roots don't keep the substrate stirred in that area. If your roots start turning black and your tank starts smelling like rotten eggs, then worry. 

Check out this thread...and others by searching H2S
http://www.aquaticplantcentral.com/forumapc/el-natural/47918-bubbles-rising-substrate.html


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## LordSul (Mar 17, 2006)

Hi helenf,

I don have any knowledge or experience in "El Natural", however I had a similar thing in an earlier tank of mine. 
If its not air trapped under the substrate from the first setup, I am afraid it might be H2S (hydrogen sulphide) from the anaerobic bacteria. Thats what these bacteria produce when theres no O2 about.
If you are using regular pot soil you are more to come across this gas I think.

This gas is no harm to fish or the plants *only* if you dont distrurb the substrate. The small bubbling wont be dangerous. However if you disturb the substrate and the deep soil you will have some pretty stressfull fish. :faint2:

Hope this helps


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## rohape (Feb 7, 2005)

To go off LordSul's post. H2S can also harm the roots of your plants. Don't fret, here's the trick.
Poke your substrate. H2S is not so harmful in small doses. Once a day or so, just poke your soil a little to release these gasses. It's a naturally occurring process. H2S is just the result of detritus breakdown.


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## helenf (Mar 24, 2008)

Thanks everyone.

I am reassured, and I will try poking the substrate some.


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## dwalstad (Apr 14, 2006)

Hi Folks,

The substrate in my new 50 gal setup is bubbling like crazy-- bubbles released every few minutes. The gas released is probably relatively harmless CO2, methane, and hydrogen (or a combination of all three). Please don't assume bubbles are just toxic H2S. Bubbling is good, because it naturally stirs up the substrate and introduces oxygen-containing water.

Toxic H2S generation requires that there be lots of sulfates in the water. Marine aquariums are very vulnerable, because ocean water contains tons of sulfates. Most freshwater/tapwater contains very little sulfates. Only if the soil contains sulfate fertilizers is there a problem in freshwater aquariums.

That said, poking the substrate never hurts.


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