pockets anaerobic gas are no myth....unfortunately

Tom, the gas is hydrogen sulfide. OrionGirl, what they are metabolizing is not nitrogen in any form but sulfate to sulfide. They only do it when nitrate is exhausted. Other bacteria in the same community are making a living oxydizing sulfide back to sulfate. All happening quite deep, and in a sediment that remains undisturbed, like gregga's.

"Burps" from the gravel, if it's deep and also organically enriched, could also be methane, which isn't very soluble. But isn't the likeliest "burp" gas just carbon dioxide? Or would CO2 always remain in solution?

If gregga's fish died of H2S poisoning, the unmistakable, gag-making odor would have filled the room. Hydrogen sulfide is not merely skanky-smelling. It's as bad as shaking ammonia with bleach. Other nasty sulfurous smells, like onions gone rotten, are thiols a.k.a. mercaptans.

What about the alternative possibility? That normal processes of bioacidification depleted the carbonate buffer and pH had dropped; harmless NH4 had built up, since nitrifiers go dormant at pH in the low sixes; then when most of the water was removed in order to shift this 20-gal. tank and was replaced with fresh, the buffering was instantly renewed, NH4 converted to NH3, and the fish were overcome with ammonia poisoning. What is sometimes called "Old Tank Syndrome."
 
nice work wetman

The authoritive tone and use of words I don't understand definitely makes me think you are right:) .

Could NH4 really be converted into NH3 so quickly that the entire tank-o-fishies die off in 30 seconds? If the conversion is a chemical one (not needing bacteria), then I can see it and do not doubt you have explained the disaster.
 
You'll want confirmation, but NH4 is ammonium, while NH3 is ammonia. The additional hydrogen atom in NH4 prevents it from bonding with fish gills, which is why products such as amquel can be used to detox chlorine--it pulls the chlorine apart, which results in ammonia, and then adds a hydrogen atom to the ammonia. Bacteria can (I think) use either form, but only ammonia is toxic to fish.

Did I get that right? :)
 
The authoritive tone and use of words I don't understand definitely makes me think you are right .
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All in favour say aye. *AYE!* The ayes have it. Wetman is correct. :D
 
May I nay?

The nitrate->nitrite reducers, and the nitrite->ammonia reducers, plus the ammonia-N2 reducers are anaerobic, that is the they operate in conditions of very low oxygen tension but not absloutely oxygen-free. The sulfate->sulfide group are absolutely anoxic, not just anaerobic - these are two different culture conditions.

The two commonest gases released from substrates are CO2 (so that part is potentially correct) and N2. I don't know which is really more frequent. Methane and H2S (which is, as wetman NY stated, hydrogen sulfide) require more extreme conditions and are most often in tanks oxidized before they escape the substrate unless disturbed.

I also strongly qustion the likelihood or frequency of ammonium to ammonia change sufficient to kill fish. unless there is already significant ammonia reading in the tank, and you take the pH from below 6 to >10, it just isn't that big an issue. I would hope nobody here would do as much a log change in pH, much less four logs. No fish would survive that anyway. even the poorest of the hobby literature suggests no more than 0.2 pH change at once. The ammonium to ammonia shift from that would be undetectable.
 
ummmmmm.........sorry I started this........:rolleyes:
For what it is worth, the substrate in question was crushed coral.

On a happier note, the Mbamba female released about 15-16 fry tonight.. You're all aunts and uncles...........


Gregg
 
Prevention?

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Lots of good info here, but what's the best way to keep the "build-up" from happening? Would using something like an ice pick to disrupt the gravel deeply on some kind of a schedule prevent it??
Using large gravel for substrate is not an option for me...
 
Originally posted by gregga
ummmmmm.........sorry I started this........:rolleyes:
For what it is worth, the substrate in question was crushed coral.

On a happier note, the Mbamba female released about 15-16 fry tonight.. You're all aunts and uncles...........


Gregg
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Don't be sorry. This is the type of challenge many of us enjoy digging into, whether it is determining what the problem truly is or just trying to keep up as we learn.

I agree with Joe. There is something for us all to benefit from here if we can prevent it from happening in our own tanks. I am somewhat concerned for my own tank because my planted substrate is a home recipe. What can we do to prevent a "build-up" of this nature from occuring?
 
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