# CO2 and yeast



## Vasudeva (Oct 29, 2009)

hi i am planning on setting up a heavily planyed tank with strong light. I dont know much about co2, but i know i cant afford to buy a large setup. i have heard of supplementing with yeast has anyone tried this and where could i go to find out more


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## flashbang009 (Aug 6, 2009)

Basically you're creating a yeast+sugar reaction and it creates CO2. Easiest way for me was to go buy a gallon water jug, with a screw on cap, and drill a hole in the cap just smaller than airline tubing. Then run the airline tubing into a filter/powerhead intake.

This article shows some other techniques and recipes. Let me know if you need any more help.

DIY CO2 will have to be replenished/the mixture dumped about every 2 to 3 weeks, depending on your "recipe" (sugar to yeast ratio).

How big of a tank will it be?


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## Vasudeva (Oct 29, 2009)

this tank will be 50 gallons


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## flashbang009 (Aug 6, 2009)

Ok. Most will tell you thats about the biggest you can go with DIY Co2. I tried it on my 75 gallon. Went with three one gallon jugs, and it was still almost not enough. Three would easily do it for you, but you could probably get away with two one gallon jugs. You have to adjust the recipes accordingly too.


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## Vasudeva (Oct 29, 2009)

I have heard of people using only one 2 liter soda bottle on a 50 gallon you are telling me i should use 3?


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## flashbang009 (Aug 6, 2009)

3 one GALLON containers haha. you can try one 2 liter, i just don't know how you would get anywhere close to the amount of Co2 you wanted. Unless I'm completely off... You could probably use 1 or 2 one gallons.


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## huaidan (Mar 6, 2010)

I have a 2 liter bottle yeast+sugar water hooked up to a powerhead in my 100 gal. It lets out a spritz of pure co2 every 30 seconds or so. There's no other source of air bubbles, and my co2 is airtight, no leaks. With thousands of microbubbles of pure co2 floating around (not to mention on top) my tanks persistently, how can I not be at saturation? I can't imagine putting any more co2 in there without it looking like soda water. Plants are looking good, really filling out and putting on beautiful foliage, including a slow-growing giant anubias, in just a few days.

Now, admittedly, I don't have a co2 test kit. However, other evidence shows that my 2 liter bottle setup with my 100 gal tank may be enough.

What I'm using in my bottle is 1 pound sugar, fill to 4/5 with water, wine-maker's yeast, and a tablespoon of yeast nutrient. I make wine at home, so I'm putting what I have to good use.
Comments?


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## Reamer (Mar 3, 2010)

i know alot of people do use yest for CO2. but personly it scares me as i dont know when Aerobic respiration ends and the fermentation starts, and i dont want to get my fishy friends drunk...


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## huaidan (Mar 6, 2010)

Considering that the yeast and sugar is kept in a separate container outside of the aquarium, and what's being introduced into the aquarium is only the gas feed, then these worries are completely unfounded. Yeast either produce co2, or no gas at all.

In answer to aerobic respiration/fermentation, yeats will produce co2 either way. However, yeast will only use aerobic respiration in the presence of oxygen, which shouldn't happen if your yeast/sugar setup is airtight. Brewers often use aerobic respiration (an aerated mix) at the beginning of brewing, as this allows the yeast to populate rapidly and vigorously. As the oxygen is consumed, the yeast switch to fermentation, which produces alcohol as a by-product.

In a proper yeast/sugar setup, no yeast/sugar/water/alcohol should enter the aquarium. The only thing that should be going into your aquarium is the effluent co2.


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## flashbang009 (Aug 6, 2009)

Exactly. And to avoid any further worries, put a check valve to stop the flow from reversing (i.e. tank to yeast mix).


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## dirtyted (Mar 5, 2010)

depending on how your setup is also. Mine for instance is in the living room and my girl would be upset if there were unsightly diy 2 liter pepsi bottles behind the tank. You can put together a neater looking version made from pvc for free if you know a plumber (he will probably throw out more than you would need) or about 20 bucks home depot. You can also be pretty sure to not have any leaks.


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## huaidan (Mar 6, 2010)

That's what's nice, the bottle fits in the cabinet stand and I run the tube up the back so it's invisible.

It's day 4 of co2, still nice, hornwort is exploding in roots and side shoots. A new red sword I added 2 days ago is really growing nicely. On the bad side, I'm getting a massive die-off of brown algae, so everything's covered with an ashy-gray debris. When it looks nicer, I'll post some pics.


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## dtezz (Mar 8, 2010)

Vasudeva said:


> hi i am planning on setting up a heavily planyed tank with strong light. I dont know much about co2, but i know i cant afford to buy a large setup. i have heard of supplementing with yeast has anyone tried this and where could i go to find out more


do a google search on "Do it Yourself Aquarium CO2 injectors". i found an article on constrution and recipes to produce CO2. The only downside, is that you can't control the exact amount of CO2 entering the water, but do believe that the amount a single 2 liter produces is not sufficient to cause harm above a 50 gallon tank. i am running 2 on a 75 gallon newly planted aquarium and have had no negligible affects. i hope this helps.


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## flashbang009 (Aug 6, 2009)

I don't even think a 2 liter could "overdose" a 20 gallon tank.


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## Reamer (Mar 3, 2010)

@huaidan

this is 100% true if there is no way the alcohol is evaporating, but guess what it is so ya, that why i will not use a yeast set up, *i am by no means a person to ask about fish tanks*, but i do know a thing or 2 about yeast.

yeast make the most CO2 86°-98°F, and that is way more then you need to evaporate some Ethanol,

many people have done it with no problems, but at what point do you see there in a problem? 
the amount of alcohol that would go in the tank is more then likely not going kill your fish, just make then uncomfortable able and may lower there immune system.

you can do it if you want, but personally i don't want to risk the off chances that i'm poising my fish.

just my thought on the subject...


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## huaidan (Mar 6, 2010)

Interesting point about alcohol evaporation. This problem would indeed involve temperature (I keep mine at room temperature, which now ranges between 15 and 20 c), the concentration of alcohol in the solution, which would gradually increase to about 15%, rate of infusion, partial pressure of EtOH in co2, and the volume of water and temperature into which the co2 is being injected. Another point of inquiry would be whether fish or plants absorb more EtOH, and the effects on both.
Any chemistry whizzes up to the task?

For comparison, a BAC of .01 would be equivalent to a concentration of 100 ppm. I don't think mine will get nearly that high, but a crack chemistry student could prove me wrong.

Edit:

Being a brewer myself, I've should have taken into account that heat, light, oxidation, and bacterial action will all break down highly volatile EtOH molecules. That's why alcoholic beverages should be stored in a cool dark place in a clean airtight container. Otherwise, it will change to vinegar. I genuinely don't think an EtOH molecule would survive that long in the aquarium. What might occur would be similar to cycling: A bacteria species would take advantage of the alcohol and keep it at a level equal to ammonia or nitrites, effectively 0. Maybe I'm foolishly optimisic, but I see EtOH as a natural by-product or intermediaryof many metabolic pathways existing in nature. I think it can be accounted for in the ecological balance sheet. However, social ramifications still exist, so I'll keep an eye out for unruly, criminal behavior, rises in unemployment, or incidents of teen pregnancy among my fish.


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## flashbang009 (Aug 6, 2009)

All i know is I've never seen a documented instance of someones fish dying or showing signs of stress or disease after starting a DIY CO2 regimen. If someone cares to correct my assertion, i would welcome it with curiosity.


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## huaidan (Mar 6, 2010)

I keep getting tempted to bubble air into the water so my fish can breath, because I see a whole lot of co2 floating around my tank, and I can't help but thinking that must make things uncomfortable for my fish. However, given the high rate of growth of most of my plants, most of that must be converted to o2, so i needn't add anymore. My fish are happy, active, and showing absolutely no sign of respiratory stress, even when I have the temperature up to 30 (I've since taken it back down to 27), despite swimming in a virtual foam of co2.

The reasoning goes like this: since fish can't produce enough co2 for plants, it must mean the plants are using co2 at a faster rate than the fish can produce. Hence, the plants are producing more 02 than the fish consume. It balances out stoichiometricly:

fish: ch2o + o2 = h20 + co2
plants: h20 + co2 = ch2o + 02

Yes, I am aware that plants also use o2, but overall produce more o2 as they gain mass. Simply, if there's a net consumption of co2 (evidenced by the NEED TO ADD co2), then there's a net production of o2. I just cite stoichiometry so as to demonstrate, with the right balance of plants to fish, introducing co2 will result in more o2 for your fish. In business, it would be like maintaining a profit margin to reinvest in new growth. Ecology and business have more than one thing in common.


I can't wait until I can skip all the conjecture and post some pics. Right now I've got the last of the brown algae clearing up, and I just got around to adding some chelated irons and trace elements yesterday.
When you start adding co2, be prepared for this: the new rapid growth, once held in check by the bottleneck in the supply of co2, will hit another bottleneck in mineral depletion, quite possibly iron depletion, as it was in my case. I started getting explosive, new whitish-pink growth on many of my plants. 24 hours after dosing on minerals, the ceratophyllum's growing tips are starting to green up a bit. It's only 2 weeks old, a bit rough now, but time will tell ultimately.

I will say, all in all, compressed co2 would without question be the best alternative if you're seeking results. However, for myself, much of the satisfaction I get from it is in seeking, as much as possible, a wholly organic DIY approach to maintaining an ecological balance. If I feasibly could, I'd pipe in sunlight from outdoors, but I have to use electrical power for the powerheads anyway, don't really see any way around that. So really, all I'm putting in is electricity for lights and powerheads, fish food, trace minerals, and sugar for the yeast. Since I'm not drinking the stuff, I can recycle the yeast, no problems. And I'm considering using the (cheap) fish food as yeast nutrient, which gives the yeast a boost in their metabolism of the sugar.


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## huaidan (Mar 6, 2010)

Update: My aquarium water without co2 stands at pH 7.2. I haven't added any chemical buffers, so that pH value is pretty accurate. Assuming no added co2, in normal aerated aquarium water containing fish,has co2 content of about 4ppm, this means a KH of about 2.2, according to http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm.
After bubbling co2 from my 5 liter yeast and sugar into a powerhead, I've been watching the pH gradually fall. Today it stands at 6.5. Any lower might be detrimental. According to the CO2 / KH / pH table, this puts my co2 at about 20ppm. In a 100 gal/380 liter tank.

So, using yeast/co2 alone apparently can produce enough co2 for a large tank, hypothetically at least. However, I'll have to keep an eye on regulating it. If the pH goes too low, could be problems.

Note: The pH really started going down when I cooled my tank from 30 degrees to 25 centigrade. Gas, including co2, is nearly insoluble at temperatures approaching 30. 5 degrees makes a big difference in gas solubility, which increases at lower temperatures.

Hence it might be possible to regulate pH by changing the temperature? Interesting.


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