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Foul smell and yellow water


23 Jun 2022
Czech Republic
sulphidogenesis is rather rare in nature.
I'm perplexed. I too regularly read scientific papers on natural ecology, and in my opinion sulfate reduction occurs wherever sulfates are present. In the oceans, it ubiquitous. It occurs in ponds regularly.
Yes, in peat bogs it may be insignificant if the water is very sparsely mineralized, and therefore sulfates are present in meager quantity. Methanogenesis occurs in such places instead.
I am less open minded to the possibility that it could form in aquariums because I tend to think that substrates are likely to be permeable to dissolved oxygen and that the chemical conditions for microbial sulphidogenesis are unfavourable and would probably take a very long time to develop.
I hate to disagree with you, @Simon Cole , really. Oxygen penetrates as deep as biological oxygen demand allows. Other factors like coarseness of the sediment or water flow above the sediment are secondary factors.
In commercial substrates containing lots of easily degradable organic matter BOD is very high, oxygen cannot penetrate very deep and anaerobic activity is huge. Sulfate reduction (to sulfide) occurs.
When hydrogen sulfide moves upward it gets oxidized either biotically (faster) or abiotically before it reaches the water column. That's the normal state of affairs. But if the BOD is too high, the boundary between oxic and suboxic zone is above the sediment and the disaster happens - hydrogen sulfide leaks into water column. Obviously, this is what happened to thread starter.
In our tanks, sulfate reduction is often relegated to very deep zones not because of deep oxygen penetration but because nitrates are abundant, nitrate reduction zone (denitrification) is huge and only below this zone sulfate reduction may occur.

Simon Cole

25 Dec 2018
As I wrote, I am still open-minded about magnitude of this process natural freshwater ecosystems, but I am not convinced that there is adequate <evidence>.
Direct evidence for atmospheric hydrogen sulphide emissions from natural freshwater systems can be rather sporadic, and often these measurements are either undetectable or very low.
There is also the suggestion that <plants are emitting most of these gases> as opposed to the water itself.

In terms of aquariums, I am still sceptical. As I proposed, test the potential for your aquarium water to generate hydrogen sulphide, then make assumptions.
I would expect that most ionic sulphur species can diffuse readily into the water column where they are oxidised. I do not foresee aquarium water columns as having the correct reducing conditions to enable hydrogen sulphide to survive for very long when it can diffuse between zones. I think it is plausible that sulphate esters and other organic sulphate molecules (including methyl mercaptans, carbonyl sulphide, dimethyl sulphide, carbon disulphide, dimethyl disulphide) can cause these smells, if sulphidogenesis is the mechanism.

My historical perception does not typically diminish in the face of introduced conjecture. We may well hold different opinions over time, but I am not that bothered about agreeing over a hypothesis, and it's not very fair to imply that a disagreement exists simply because my historical perception does not support a particular position that you hold today. If I had to form an agreement with you, then it would be that I am dubious, sceptical, unresolved, open-minded, and ambivalent, in that order. The academic community is a long way off persuading me that there are obvious disasters waiting to happen. I am uncertain whether what you have said is even hypothetically possible. No offence taken, I am still grateful for your comment :thumbup:
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