Consistency Deficiency

[Hufsa]

I can understand why you might think that @_Maq_ , its actually a layer of weakly colored blue green algae or something of that sort. It only grows right up against the glass, and comes off in filmy sheets if i run my finger along the glass. I used to remove it once or twice a year, but I haven't wanted to disturb the crypts that grow nearby this year. The layer has become more intense this year but im just monitoring it to see if it goes away on its own.
Are you adamant that it is iron sulfide?

 

[_Maq_]

Are you adamant that it is iron sulfide?

Well, the cyanobacteria are conspicuously missing in the highest layer of the substrate... and it really looks bible black, though photography may distort coloration, of course.
But I don't find it outright bad, in the first place. It's quite natural. And the crypts obviously like it! (Ooh, how I envy you!)

 

[Hufsa]

I'll pull some of the brownblack stuff up tomorrow where there are no crypts and take a few pictures, we'll take a good look at it. In a few areas it is more like the traditional bluegreen color.
I keep kuhli loaches that keep the upper 1 centimeter of sand pretty pristine, which may account for the strict cut-off 😊

 

[jaypeecee]

It's clear that deeper layers of your substrate are full of sulfides, mainly iron sulfide (black coloration). Are you aware of that?

Hi @_Maq_

I'm intrigued. How did you arrive at the above conclusion?

JPC

 

[jaypeecee]

Hi @_Maq_

I think I may know the answer to my question and I will gladly explain the reason for this question. But I don't want to 'put words in your mouth', if you're familiar with this expression.

JPC

 

[_Maq_]

I'm intrigued. How did you arrive at the above conclusion?

Redox cascade. Bacteria respire what's the best available terminal electron acceptor (TEA). 1. oxygen, 2. nitrate, 3. ferric iron, 4. sulfate, 5. methanogenesis. When sulfate is respired, hydrogen sulfide is the result, which readily reacts with present transition metals, mostly iron. Iron sulfide is the source of black colour.

 

[Hufsa]

Took some pictures today, interested to hear what the jury has to say


Closer up photo taken with flash of some of the sand front, theres a band of green algae at the very top where I think they have found a niche, its close enough to the surface to get ok circulation but still under the sand so the otos cant eat it.
Slightly lower down there are sporadic patches of typical cyanobacteria, although they make up a relatively low portion of the total.
Then below that the majority is occupied by the brownblack thing.
I would be really surprised if this brownblack thing is not something that requires light to survive, otherwise why on earth would it only be in a very thin layer right up against the glass, and not throughout the entirety of the substrate?


I pulled up a flake of it so you can see. Its not very thick, only a milimeter or so. The sand grains closest to the brownblack thing was attached to it like sprinkles on cake icing.


The sand behind it is totally clear although a little dusty, very small particles of matter settles into the substrate over time, even with such fine sand.


A pic from the side of the tank, theres very fine mesh bags filled with pebbles under the sand that is banked in the back, because I didnt want to make the sand too thick.
You can see some colonies of various stuff making their home here.




Whatever the brownblack thing is, the shrimp and snails find it pretty tasty. Do shrimp eat iron sulfide?

I had to go out for a bit and when I got back home again they had eaten all of it

Im no longer quite convinced its discolored cyano, but its gotta be some other bacteria/algae thing imo.
Let me know what you think @_Maq_ @jaypeecee and anyone else who might know what it is

 

[jaypeecee]

Hi @_Maq_, @Hufsa & Everyone

In our tanks, the species of Cyanobacteria that are sometimes seen are invariably blue-green in colour. And that explains the acronym 'BGA' for Blue-Green Algae. As we now know, it is not an algae, but a form of bacteria. In one of my tanks, I identified this as Oscillatoria, probably O. princeps. Very recently, I discovered that there is a species of Oscillatoria that doesn't need a source of oxygen to flourish. And this is O. limnetica. It can use hydrogen sulphide to photosynthesize. I deduce that this is what is being seen in Hufsa's tank.

JPC

 

[LMuhlen]

I have the same black coat growing in my tank inside the substrate, close to the glass. Sometimes I pull some of it out with my finger and it feels like ciano, maybe a little dried out. My SAEs go crazy with it, they eat it all.

 

[jaypeecee]

And this is O. limnetica. It uses sulphur instead of oxygen to photosynthesize. I deduce that this is what is being seen in Hufsa's tank.

Hi @_Maq_ , @Hufsa & Everyone

I wrote the above (post #748) before seeing the photo above. Need more time to study this.

JPC

 

[Hufsa]

Need more time to study this.

Appreciate your help as always JPC

What makes me doubt that its cyano is that I didnt think shrimp and snails were fond of eating cyano? To be honest I have never had cyanobacteria above the substrate, so I dont have any first hand experience with it. But I have gotten the impression that clean up crews dont really eat the traditional blue green stuff? Would anyone struggle with cyano if the shrimp found it as tasty as this brownblack thing?

 

[jaypeecee]

When sulfate is respired, hydrogen sulfide is the result

Hi Everyone,

If hydrogen sulphide (H2S) is released, I would expect the classic 'rotten eggs' odour.

JPC

 

[jaypeecee]

Hi Everyone,

Time for a break. Back later.

JPC

 

[_Maq_]

@Hufsa , thanks for nice photo-documentation. Now I rather believe it's a bacterial colony, quite possibly sulfate-reducing or sulfide-oxidizing.
Yet one more note: Sometimes when rearranging hardscape, you turn over a stone and its surface is black. But not the sand beneath the stone. From that I deduce that iron sulfide tends to adsorb to such surfaces, but perhaps not iron sulfide itself but bacteria which cause its creation.
As for cyanobacteria, I know from books that not all of them are actually blue-green; very different colours are possible. But don't ask me about details.

If hydrogen sulphide (H2S) is released, I would expect the classic 'rotten eggs' odour.

Not necessarily, I think. Hydrogen sulfide gets quickly oxidized upon entering oxic layer of the substrate. Apart from that there are bacteria which oxidize H2S or HS-.

 

[jaypeecee]

To be honest I have never had cyanobacteria above the substrate, so I dont have any first hand experience with it. But I have gotten the impression that clean up crews dont really eat the traditional blue green stuff?

Hi @Hufsa

Correct. I don't know of any fish, shrimp or snails that eat Oscillatoria - and survive. It's quite something that you've managed to avoid 'BGA'. That tells its own story. I'd be interested in knowing more about your setup(s) in terms of water parameters, use of CO2, filtration, lighting, etc. Perhaps it's the Norwegian water?

JPC

 

[Hufsa]

Correct. I don't know of any fish, shrimp or snails that eat Oscillatoria - and survive.

That should rule out that then 🤔

It's quite something that you've managed to avoid 'BGA'. That tells its own story.

Is it? I didnt think it was particularly remarkable to be honest, I thought every aquarist had one or two types of algae that they tend to struggle with, and some they never really see much of.
The ones ive had as my most "faithful companions" are BBA and some thread algae

I'd be interested in knowing more about your setup(s) in terms of water parameters, use of CO2, filtration, lighting, etc.

I recently did a little write-up on my water values for Maq, you can find it here.
For the rest you may have to hunt a bit, although maybe it would be cruel of me to send people to read through all my ramblings hunting for useful info 😅

Perhaps it's the Norwegian water?

Maybe! Although it could just be a side-effect of the Cryptocoryne viagra

 

[jaypeecee]

Hydrogen sulfide gets quickly oxidized upon entering oxic layer of the substrate

Hi @_Maq_

I don't know much about substrates. Is there a distinct oxic layer within the substrate? If there are plants rooted in the substrate, do these not oxidize zones within the substrate?

JPC

 

[_Maq_]

Is there a distinct oxic layer within the substrate? If there are plants rooted in the substrate, do these not oxidize zones within the substrate?

Oxygen penetrates the substrate only millimeters deep, that's the oxic layer. Beneath is a suboxic layer where bacteria respire nitrate. Beneath that, anoxic layer follows.
Yes, plants oxidize the rhizosphere, but only 1 to 4 mm max around the roots. In that way they create a very important microcosm inhabited by many bacteria. Many essential microbial processes occur near the roots.

 

[ElleDee]

Oxygen penetrates the substrate only millimeters deep, that's the oxic layer. Beneath is a suboxic layer where bacteria respire nitrate. Beneath that, anoxic layer follows.
Yes, plants oxidize the rhizosphere, but only 1 to 4 mm max around the roots. In that way they create a very important microcosm inhabited by many bacteria. Many essential microbial processes occur near the roots.

What is the basis for the stated depth of "only millimeters"? Is that supposed to account for differences in substrate, the amount of flow present, and any bioturbation from fauna?

 

[_Maq_]

What is the basis for the stated depth of "only millimeters"?

Science. Scientific papers. Water does not flow in the substrate. Only dissolved substances diffuse.
Yes bioturbation, and other factors may influence it, but not in the orders; it's still millimeters.