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El Natural Diana Walstad's low-maintenance, soil-based 'El Natural' method for keeping plants and fish.

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Old 09-07-2004, 11:31 AM   #1 (permalink)
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I had potted up some plants and was moving them into the goldie tank when I noticed the sour smell. Smelled like a terrestrial plant does when it sits in water too long and starts rotting. I'm sure it's bacterial... anaerobic processes most likely. Need to go read your book *again*, but I thought I'd be lazy and just ask.

What is causing that smell?
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Old 09-07-2004, 11:31 AM   #2 (permalink)
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I had potted up some plants and was moving them into the goldie tank when I noticed the sour smell. Smelled like a terrestrial plant does when it sits in water too long and starts rotting. I'm sure it's bacterial... anaerobic processes most likely. Need to go read your book *again*, but I thought I'd be lazy and just ask.

What is causing that smell?
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Old 09-07-2004, 02:01 PM   #3 (permalink)
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It's probably from H2S (hydrogen sulfide), a stinky and fairly toxic gas. If there's enough H2S, it will stunt plants or kill fish. One symptom is blackened plant roots.

However, some plants still thrive in stinky, H2S substrates. Let plant growth and the condition of their roots guide you.

Something to keep in mind is that iron will neutralize H2S by forming iron sulfides. Thus, an iron-rich substrate will release less H2S. Potting soil, which doesn't have much iron and is loaded with organic matter, will release more H2S.
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Old 09-15-2004, 07:03 AM   #4 (permalink)
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I've been looking for info on the mechanisms thru which hydrogen sulfide is toxic to fish, but haven't been able to find anything specific. Does anyone know it's pathophysiology?
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Old 09-16-2004, 12:01 PM   #5 (permalink)
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Thank you for asking such a question that I would love to answer. I briefly describe the mechanism of H2S toxicity on page 133 in my book and cite a couple scientific references.

However, without getting into too much scientific mumbo jumbo... I can understand why H2S would be very toxic.

First, H2S like ammonia is an uncharged gas. Because of this one fundamental fact, H2S and NH3 can rapidly pass (without regulation) through cell membranes into the cell (In contrast, charged particles like NO3- and sulfate can't, because they have an electrical charge that doesn't allow them to penetrate the lipid barrier). The cell membrane is made up of lipids, which are fat-like substances that repel water and all electrically charged particles, that is, salts). Therefore, ALL cells (of plants, humans, fish, etc) have a tough time keeping H2S and NH3 gases from coming into their cells.

Second, H2S (hydrogen sulfide) rapidly and strongly reacts with metal ions to form metal sulfide compounds. Many cellular enzymes contain a metal like iron or zinc or copper as their "active center". The sulfide reacts with these metals to form iron sulfide, zinc sulfide, copper sulfide... and presto the enzyme is inactivated. Since enzymes are the workhorses of cells, the presence of H2S inside the cell would be devastating to cells.

Ammonia has a different mechanism. Ammonia gas getting into cells (again a neutral gas flooding the cell) inevitably causes the cellular pH to increase. The pH increase causes cellular enzymes, most of which like to work at physiological pH (7.2 to 7.4), to work much less effectively. At some point the cell can't function anymore and dies.

Thus, ammonia and H2S are toxic to all organisms.
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Old 09-16-2004, 07:57 PM   #6 (permalink)
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I sifted the last topsoil I used. That should help.

Yea, that's pretty muchly what I found today, this article focused on an enzyme in mitochondria resposible for conversion of glucose to energy (ATP).

Found the abstract for an article that's relevant: Torrans EL, Clemens HP. Physiological and biochemical effects of acute exposure of fish to hydrogen sulfide. Comparative biochemistry and physiology, 1982, 71:183-190.

Pretty deep tho.
The channel catfish exposed to 0.5 mg/l H2S at 20 degrees C showed rapid respiration, then they stopped breathing and died. Looks like it inhibited cytochrome oxidase activity in the brain and gills and increased blood lactate levels (latate builds up when the cells run out of O2 and use an anaerobic process to convert glucose to energy). Sulfide-inhibited brain cytochrome oxidase recovered from a 50% inhibition to control levels in channel catfish after 6 hr in freshwater at 10 degrees C.

That's interesting... fish with methemoglobinemia from nitrIte binding up the hemoglobin in red blood cells showed less inhibiiton of cytochrome oxidase. I wonder if hemoglobin plays some role in the transport of H2S...

Now what the heck is cytochrome oxidase. ok, according to your dictionary.com
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>cytochrome oxidase is An oxidizing enzyme containing iron and a porphyrin, found in mitochondria and important in cell respiration as an agent of electron transfer from certain cytochrome molecules to oxygen molecules. <HR></BLOCKQUOTE>

I think I get it. H2S results in not enough cytochrome oxidase and the cells have to switch to anaerobic processes to turn glucose into energy (ATP) and that results in lactate buildup. So even if O2 is available, they can't use it if enough cytochrome oxidase is inactivated.

Oh this is interesting (I've been reading up on bouyancy issues in goldies and this turned up with a search for lactate).
Lactate apparently had a role in the venous transfer of gasses from the blood to the swimbladder. Apparently lactate lowers blood pH causing hemoglobin to dump its O2, increasing the O2 saturation in the blood and allowing O2 to flow into the swimbladder.
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Old 09-18-2004, 05:29 AM   #7 (permalink)
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Please! We've gotten too deep. Even I'm lost now.

We will lose our readers with this level of detail. This is why hobbyists often get turned off by the minutiae of scientific studies.

My point in explaining mechanism is that H2S (like ammonia) is a GENERAL toxin that will affect many, many cellular enzymes not just cytochrome oxidase. And it will affect all living things.

In the real world of aquariums, it will harm aquarium plant roots (blackened, stunted , mushy roots) if the substrate gets too anaerobic (thick layer of potting soil or too much organic matter). Here's where a few burrowing Tubifex worms might help!

I think it is the reason gravel-only substrates become toxic to fish if the gravel is not cleaned frequently. Organic matter (over many months) settles at bottom of gravel and starts generating H2S. Clown loaches and other bottom-dwelling fish especially get sick.
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Old 10-04-2004, 04:09 PM   #8 (permalink)
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<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> We will lose our readers with this level of detail. This is why hobbyists often get turned off by the minutiae of scientific studies. <HR></BLOCKQUOTE>

I've found this to mostly dominate the freshwater end of the hobby. In my experience, the opposite is generally true for reefkeepers: the more minutiae, the better. Not sure why freshies haven't jumped more into the scientific/biologic aspects of what's going on in their tanks. I guess many reefkeepers begin with an interest in the ocean and the processes which occur in a marine habitat...then set up a reef tank. Freshwater tanks are so 'easy,' anyone can just go set a tank up and chuck in some fish and things run relatively smoothly...THEN they start to wonder what's going on in there. Reverse process of interest, maybe?

Sorry for the tangent.
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Old 10-04-2004, 04:21 PM   #9 (permalink)
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Interesting. Definitely some self-selection going on.

I personally like to understand why things work. Just found a graduate level fish physiology course online from University of Tennessee by Dr. Richard Strange. http://web.utk.edu/~rstrange/wfs550/entry3.html
He's put together a CD that several of us on another board are getting together and ordering. http://bellsouthpwp.net/r/s/rstrange/

That should help get us more geeked up.
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Old 10-05-2004, 04:07 AM   #10 (permalink)
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I took a look at the fish physiology website. It looks interesting. Thanks for posting it.
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