Gas Bubbles In Gravel

[Elrohirthehasty]

I've always assumed the gas bubbles that build up in my relatively coarse gravel was CO2 made by bacteria.  Is this true? And is this a problem?  I've taken it to mean, "hey, you need to clean your tank remember".  Whenever I clean, I knock a fair bit of it out and it takes a while to build up again.  

 

[techen]

It rarely happens in gravel, It's more in sand as its finely compacted. It can become a issue when a lot of these bubbles are uncovered which can lead to fish deaths.

 

[Elrohirthehasty]

Don't they just float to the surface and go away when disturbed? Or does enough dissolve into the water to cause a sudden chemistry change?

 

[Chad]

Both really. When they rise to the surface the gas is released not only into the air but partly into the water. Enough of this and it will kill fish. Regular siphoning of the gravel to remove organic particles trapped there will prevent this.

 

[Elrohirthehasty]

Makes sense.  I figured I do enough siphoning because I haven't killed anything from that yet!

 

[fluttermoth]

Depends on how many bubbles you're getting.
 
If it's only a very few, then that's pretty normal; if there's lots, every time you gravel clean, then that's a worry and you're either overfeeding or undercleaning

 

[KirkyArcher]

Why is it believed to be Co2 ? 

 

[fluttermoth]

Good point; it's almost certainly hydrogen sulfide.

 

[Chad]

Good point; it's almost certainly hydrogen sulfide.

Yes, that's what I was thinking as well. My guess as to why Co2 was mentioned is simply it's a well known gas commonly associated with bubbles.

 

[Elrohirthehasty]

I only have a rudimentary, high-school level understanding of biology.  Aren't the main gasses from protein breakdown...ammonia, carbon dioxide, and hydrogen sulfide?  So, shouldn't these bubbles be a mix?  Although ammonia is pretty volitile (high vapor pressure) and I would imagine would just dissolve or leave the tank at the top (hey, cycling).  Does hydrogen sulfide just have a low vapor pressure?  I assume we can call the water and gravel/sand a closed system since the compacted media isn't allowing bubbles to escape normally.
http/en.wikipedia.org/wiki/Chemical_process_of_decomposition

 

[Chad]

I wouldn't worry too much about what the gas is really. Deep cleaning of the gravel and control of leftover food in other ways will eliminate it regardless of which kind of gas it is. The rest is just an aside that can be hashed out once you are satisfied with how your tank is going. I don't want to side track things with an analysis of gas content in your tank.

 

[Elrohirthehasty]

I'm curious from a technical standpoint now.  What is (likely) the chemical makeup? Hmm....

 

[Chad]

We often see hydrogen sulfide in deeper sand or sometimes deeper gravel. It would be rare in shallow gravel as it requires anaerobic conditions. It's produced by bacteria that breakdown organics in low to no oxygen environments. This will often come with a rotten egg odor.
 
Co2 is a possibility depending on the substrate conditions. If you look at the article you linked it states this is more from the break down of certain sugars. There is no odor.
 
It's highly possible it could be Co2.