--------- Todd Crail wrote : 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)
---------- Nick Zarlinga wrote:
Date: Tue, 6 Sep 2005 20:47:01 -0400
From: "njz" <njz at clevelandmetroparks.com>
Subject: Re: NANFA-L-- Killer Rain, Stratification + H2S
Good job Todd!
As far as Hsulfide, I have never seen an effect on fish. It always amazed
me since I have smelled some pretty rotten stuff. I do beleive that even a
very small concentration is very potent to the olefactory senses. You have
definitely seen an effect on fish attributed to this? Nick Zarlinga
Date: Tue, 6 Sep 2005 13:03:42 -0700 (PDT)
From: Gerald Pottern <gbpottern at yahoo.com>
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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