Experiment : Added bread yeast to my planted aquarium

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ScreamingKoala

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Jun 6, 2019
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Today, I sprinkled bread yeast into my planted aquarium's waterfall.

My goals:

I'm building a low-tech, 20 gal, balanced ecosystem. My goal is to get cheap CO2 in the laziest way possible.


Here's my logic...

Yeast eat dissolved sugars and O2 (supplied by plants and waterfall)
CO2 rises (buffered by sand stone, egg shells, and the shells of all my living snails)
Yeast bloom triggers daphnia bloom (daphnia shells, I imagine, would have a buffering effect as well)
Daphnia feed betta. . .
...hakuna matata

I'll let you know how it goes.
 

Sploke

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What sugar source are you thinking the yeast is going to eat that will produce any co2?
 
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dougall

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Mar 29, 2005
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lazy would be getting a pressurized system, as large as possible, and having a pH controller to turn on and off CO2 when levels were reached.


or were you thinking cheapest.?
 

ScreamingKoala

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Jun 6, 2019
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What sugar source are you thinking the yeast is going to eat that will produce any co2?

Plants and algae are little sugar factories. Like a sugar cube dispersing in coffee, the concentrated sugars in the plant cells diffuse out into the water column. A damaged cell here, a cryt-melt there....sugar inevitably leaks.

The big thing I'm wonder now is if wild yeast already ate it. If the tank was already at equilibrium, adding more yeast just makes dead yeast.
 

ScreamingKoala

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Jun 6, 2019
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Day 1

I know it's only been one day, but I'm calling it a bust. I'm not observing a sustained yeast bloom.

Evidence
- water is as clear as it ever was
- no yeasty "bread-in-the-bread-maker" smell.
- No substantial change in plant growth. When I inject CO2, it's quite evident.

Conclusion
- One dose of bread yeast is ineffective. The sugar levels are most likely in a state of equilibrium, where "volunteer" organisms (wild yeast, protists, etc) are consuming sugar at the same rate that it's produced.


Extending the study

Sugar-ing the tank is an option, though it's one I will not be trying. This would give wild organisms more to feed on, potentially triggering a bloom at the bottom of the food chain. I, however, am not inclined to take this risk. Unfed yeast die, and no harm is done. Over fed yeast bloom uncontrollably, and....well someone else is more than welcome to donate their tank to this noble cause.
 

OrionGirl

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No food source goes unconsumed. That's pretty much a basic rule for any environment. Sugars available are consumed by a variety of bacteria already, and I really think you are underestimating the amount of available sugar in the water column. You would need to supplement the sugar substantially, and even then, you would end up with a mess. There are several reasons why yeast CO2 is done outside the main tank. Cloudy water and excess alcohols are just one. Yeasts grow best with abundant oxygen, which means floating on top of the tank. Not pretty.
 
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Sploke

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Plants and algae are little sugar factories. Like a sugar cube dispersing in coffee, the concentrated sugars in the plant cells diffuse out into the water column. A damaged cell here, a cryt-melt there....sugar inevitably leaks.

The big thing I'm wonder now is if wild yeast already ate it. If the tank was already at equilibrium, adding more yeast just makes dead yeast.
That's not *quite* how that works. S. cerevisiae is pretty selective about its food source, and can really only use very simple sugars (glucose, fructose, sucrose). The yeast is not able to break down and process longer-chain carbohydrates on its own. While I have no idea what specific types molecules the sugars in plants are bound up in, I doubt that they are readily accessible to the yeast. If that were the case, brewing beer would be a lot easier, you could just dump grain and yeast in a bucket and dispense with all that enzyme modification to get a fermentable product.
 
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ScreamingKoala

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That's not *quite* how that works. S. cerevisiae is pretty selective about its food source, and can really only use very simple sugars (glucose, fructose, sucrose). The yeast is not able to break down and process longer-chain carbohydrates on its own. While I have no idea what specific types molecules the sugars in plants are bound up in, I doubt that they are readily accessible to the yeast. If that were the case, brewing beer would be a lot easier, you could just dump grain and yeast in a bucket and dispense with all that enzyme modification to get a fermentable product.

That's a good point. Plants are chaining their glucose up into cellulose and starch... That alone, ought to keep the vast majority of it out of the water column.

But, in the interest of science, let it be know that there is, in fact, dissolved sugar. But to OnionGirls point, it ain't much in a balanced ecosystem.
The numbers : https://aem.asm.org/content/57/11/3135.short

Roughing the numbers, my tank would have 25 millionths of a mole of sugar... not baking any cakes like that...
 
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