RE: NANFA-L-- Killer Rain, Stratification + H2S

Crail, Todd (tcrail at UTNet.UToledo.Edu)
Tue, 6 Sep 2005 21:52:23 -0400

Hi Gerald,

While H2S is definately a caustic molecule as it acts like cyanide in the
bloodstream, binding iron at certain levels that may seem low (in micrograms
per Liter)... My understanding is that it takes such a concentration of H2S to
reach the levels where LD50 tests have shown mortality in fathead minnows due
specifically to H2S (like you would literally begin to barf as it evolved from
the tank) that there would have been far more nefarious conditions in the
aquarium (such as NH4+) before the H2S was in any part, the causative agent.

I can also anecdotally vouch for the presence of H2S in systems having no
observable effect in my systems. With my deep sandbed approach, I am rotting
material continually, to the point where moving rocks sends plumes of black
nasties, and clear bubbles, without any problems. As I mentioned, I think
people are having problems in their tanks because of other issues, catch a
whiff of something rancid, and assume that was the problem, while far more
volatile and caustic chemicals are running around.

And theoretically, we also have to remember that each night in these systems,
the thermocline would break up, and the system would slowly mix back together.
This would dissipate any H2S trapped in the dissimilar chemistries as you had
mentioned, and avoid a situation where accumulations could become deadly...
Such as the mixing event in Cameroon a few years back, where a deep,
stratified volcanic lake mixed and effectively gased _everything_ within a
certain radius... Much like Dad after Thanksgiving dinner :)

Actually, I shouldn't joke, because it was quite devestating... But I couldn't
resist the analogy.

Todd
The Madness (tm)

________________________________

From: owner-nanfa-l at nanfa.org on behalf of Gerald Pottern
Sent: Tue 9/6/2005 4:03 PM
To: NANFA-List
Subject: NANFA-L-- Killer Rain, Stratification + H2S

Todd/Geoff/Nick/Moon/Mystery & killer rain sleuths - even if the hypolimnion
(cooler bottom water) of the pond wasnt anaerobic yet, there could have been a
lot of hydrogen sulfide H2S down in the detritus layer, that got churned up by
a rain-induced turn-over. You can watch fish stress out even in a well
aerated aquarium if you stir up deep dirty gravel full of aged fish poop (and
smell that H2S). Its very toxic stuff, but oxidizes or dissipates ??? pretty
quick after mixing in aerated water.
gerald -- hangin on the neuse, NC

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