Generating CO2 for an Aquarium with Yeast.

xxdaggerxx

HI everyone, this is going to be a odd question but here goes.
I have a planted tank aquarium at home, in the aquarium hobby we occasionally build our own DIY CO2 generators using a yeast, sugar and water.
An example:
Its a crude method but it works and saves us hundreds of dollars in professional CO2 equipment.
CO2 is important for in the growth of aquatic plants, and the health of these plants keep the tank and livestock happy.
Anyway, one of the issues of this method is that the yeast eventually kills it's self because it generates to much alcohol. I'm using regular supermarket yeast meant for bread btw.
Now my question is to all you yeast experts, is that a way i can prolong the longevity of the yeast (maybe indefinitely?) with out it killing itself?
i found high tolerance yeast which seems like a good idea, or even low alcohol yeast : SafBrew™ LA‑01
Do these things work in my case?
Also i read that when yeast is in a aerobic environment, they produce CO2 and water (no alcohol) is this true? If that's the case can i just pump air into my yeast-sugar mixture and reduce the alcohol levels that way?
Thanks very much for your advice!

VikeMan

I assume you're looking at LA-01 because it doesn't make a lot of alcohol. But the reason is doesn't make a lot of alcohol (in beer wort) is that it ignores complex sugars, and only ferments simple sugars. In your aquarium CO2 application, that restriction wouldn't apply. It would make just as much CO2 and alcohol as any other strain, until it reaches its ABV tolerance limit (assuming enough sugar).
But the reason you have to start over in a couple weeks is that the sugar has been used up, not really because of high alcohol. I suppose you could keep dumping sugar into the same container without talking anything out. In that case, you'll either overflow the container or stun the yeast with alcohol, whichever comes first.

Not really. If your sugar concentration is at a high enough level to make a useful amount of CO2, the yeast will mostly bypass aerobic respiration and do alcoholic fermentation instead, because of something called the Crabtree effect. Theoretically, you could maybe find a sweet spot to maximize respiration and minimize alcohol (this would also require providing yeast nutrients), but you'd still have to start again when the sugar (or space) is used up, just like you would with a "normal" setup.

hotbeer

Wouldn't a little baking soda and vinegar give you the CO2 you need for less fuss.
Otherwise I'd think you'd be getting into the management of your yeast similar to how people go about saving and reusing yeast from one beer batch to the next.
And my little CO2 inflator and cartridges for my bicycle tire wasn't 100's of dollars of equipment.

McMullan

It"s not possible to maintain yeast cells indefinitely simply with water and sugar. They are struggling with nutrient deficiencies. It should be fine using cheap baker's yeast, but, without adequate nutrients, it's going to need to be replenished regularly. Using malt extract to provide a nutritious medium for the yeast is going to be much better, but more expensive. Potentially more expensive than a small CO2 cylinder?

IslandLizard

You can harvest the yeast before the alcohol content gets too high and kills it.
Then repitch (with added nutrients) into a new batch. You may have to use 2 bottles, one active, the other for sedimentation/yeast harvesting.
Yeast mass also grows, so you could reuse the extra for additional or larger tanks, baking, etc.

SanPancho

just set yourself up with a semi-closed loop system. sugar and some cheap yeast for baking bread will be fine.
what you want is a slow and consistent rate of co2 into your tank. hopefully it will last a week if you can keep it to a cool/cold temperature. so you dont want to give the yeast nutrients, you actually want them slow and sluggish. you are better off if they take a week to eat all the sugar vs only one or two days.
so make a batch, and use only a very small amount of yeast. that will spread the action out over a longer time period. once it stops, pour off as much of the liquid as possible while leaving the yeast behind on the bottom of the bottle.
then fill it with water, shake it up well, and pour off 3/4 of the bottle into your pan or pot where you make your sugar mix. the dead yeast will get boiled and decompose, which will provided nutrients to the yeast you kept alive in the bottle.
add it back into the bottle and start the cycle again. you can probably go for a few weeks before you hit problems. at that point, just start over with fresh yeast.

marc1

If I were to do this, I'd use one of the other methods where the sugar is mixed into gelatin, so that it slows down that CO2 production and lasts longer. In the method you're showing here, the yeast is going to eat through all the sugar pretty quickly and generate a lot of CO2 at once. You don't need a lot of CO2 at once, and slowing it down should make the contraption last much longer.
Cheap bread yeast should be sufficient. The video below uses 1-2g for a month or so of CO2 production.

Bassman2003

I like your idea as fermenting yeast make a lot of CO2. One other way to look at this is to use turbo distillers yeast. It has a higher alcohol tolerance and might give you more longevity. The approach of using a little yeast and basically swaping out the fuel seems like a good approach.

SanPancho

have you tried this? from the video it looks like the gelatin sets first, then he adds yeast. that seems like it wouldnt work very well unless the yeast could somehow penetrate the gel and get to the sugars. or is he adding the yeast while the gelatin is still fairly liquid? he doesnt specify, doesnt really shake the gelatin either so im not clear.
crazy interesting idea.

z-bob

I haven't tried it but I really like that idea. (when I was doing CO2 injection for my planted tank I used a 10# compressed gas tank) It looks like the gelatin sets before you add the yeast. The sugar slowly diffuses into the yeast-water on top, and the yeast slowly penetrates the gelatin. And the yeast can probably use digest some of the protein in the gelatin for the nitrogen they need.

marc1

I've been thinking about getting an aquarium again after many years out of the hobby, so I've been casually researching it for a while. I stumbled across this CO2 method and thought it was genius.
The sugar is set in the gelatin, and the yeast is in the water above it, so the yeast takes a while to get to the sugar. I'm not sure if the yeast gets into the gelatin matrix, or if the sugar slowly diffuses into the water, or both. It looks like it keeps the CO2 production rate steady and slow compared to when the yeast has access to all of the sugar at once.
I haven't tried it, but there's to be enough online about it to make me think it's viable. It's certainly inexpensive enough to give it a shot, especially if you are already set on trying the yeast in a bottle method. If I get set up again and decide to try CO2 for the plants, I would try this myself before going the CO2 cylinder route.