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80 Posts
Discussion Starter · #1 ·
Hi everyone:biggrin: I was wondering about c02,I saw it in the aquatic center and I know what it does,but it is way to expensive.How do I make a cheaper yeast and sugar c02 injector



p.s sorry if this has been posted a million times before me

1,062 Posts
DIY CO2 can be really cheap. All you need for the most basic version is:
-2L bottle
-Airline tubing (preferably silicone)
-check valve

For this design, you drill a hole in the lid of the bottle that is slightly smaller than the diameter of the tubing. You then pull the tubing through the hole about 1/2" (pliers are nice). You then hook the check valve somewhere on the tubing between the bottle and the tank (to prevent backsiphoning of water onto your floor) and stick the end of the tubing into the aquarium somewhere.

For a little more complexity, but not too much more cost, you can add a bubble counter/gas separator. This helps to keep yeast out of your tank if it tries to get out of the 2L bottle. All you need beyond the basic version is:
-a 20 oz bottle
-more tubing

This design places the bubble counter between the 2L bottle and the check valve. Here's how you do it. Drill the same hole in the 2L bottle and pull your tubing through in the same way. Drill two holes in the cap of the 20oz bottle in the same way that you did on the 2L bottle. One of those holes is for the other end of the tubing from the 2L bottle. Pull the tubing through a few inches. The tube should reach down to the bottom of the 20oz bottle (or close). Then pull a second tube through the second hole, only about 1/2". This tube goes to your check valve and then to the aquarium like in the basic model. You then fill the 20oz bottle about half way with water and secure the lid on it.

TIP: cut the tubing at an angle so it's easier to pull through the lids.

Appx cost:
$2 for the bottles (free if you drink bottled drinks)
$3-5 for the tubing (silicone, you'll have a bit of extra)
$2 for the check valve
$3 for the sugar bag (a few month's worth of co2)
$1 for enough yeast for months

361 Posts
Read this.
D.I.Y. Yeast Based CO2

Here are some hints if you are going to go with a DIY yeast based CO2 system.

* Use juice bottles and not soda bottles. Bigger caps, larger openings, more stable.
* Drill a hole in the cap smaller than the OD of the tubing. Cut the tubing at an angle. Pull it though with pliers. Done. The seal is gas tight.
* Get a Hagen bubble counter/diffuser. Just that part. You don't need/want the rest. Use their tubing. It works fine.
* Use plain old white sugar. I prefer to use wine yeast because it works at the lower winter temperatures I keep the house and it has a much higher alcohol tolerance than bread yeast. And $1 will buy a year's supply. Also when recharging the bottles I pour off the liquid and use the bottle sludge for the next bottle. That's the yeast.

Have you seen Tara Nyberg's PowerPoint presentation about yeast for aquarium use?

If you have Powerpoint, you can view the whole presentation. If you don't, it is below this. Here is the PDF only.

What are the major expenses?
Tank and stand

How to live on the cheap.
Tanks and Stand -- buy used and pay no more than $1-2 per gallon. Re-paint stand as needed. Hammer in a few boards to make it more sturdy/look better

Lights -- use 48” electronic T8 fixtures that you can get at the hard ware store for ~$20

How to live on the cheap- substrate
Substrate -- buy plain gravel or sand (also from hard ware store esp. if you can get the no-salt sand for icy roads)
Supplement in moderation with things like peat/soil (~1cup/ square foot) ironite (~1 T/square foot),
I like to make clay balls with added nutrients and add them both before and after a tank is planted. I recently set up a tank with nothing but clay balls. And plain gravel

How to live on the cheap --CO2

I have used yeast CO2 on tanks up to 180 gal. Also 75s, 65s etc.
2 gallons of yeast changed once every 3wks to month depending on the temperature works well. I don’t rotate the bottles either.
The key to long lasting cultures is allowing them to grow and be happy. Also a little basic knowledge of yeast growth helps.

Yeast Growth/metabolism

Yeast can either produce energy by fermentation or oxidative phosphorylation (ox/phos)
Yeast greatly prefer fermentation over ox/phos and will not start ox/phos until all the sugars are converted to ethanol.
Ethanol is a good source of energy and in the presence of oxygen yeast use it up as well.
Fermentation also produces 2 CO2 molecules per molecule of sugar-- as a by product. =)

Why is just sugar and water not ideal?
When you just add sugar and water to yeast, they are essentially starving to death.
However the enzymes for converting sugar to ethanol are still in the cell and will work for a limited amount of time.
Since the cells do not have what they need to make new enzymes as cells starve/run out of enzymes the culture produces less and less CO2.

Also, we add too much sugar.
Ethanol and sugar are increasingly toxic to yeast at greater than 10% concentrations.
Therefore 2cups (~500ml) of sugar in 2L of water (~25% sugar) is unhealthy for the yeast.
It is also a waste of sugar because 10% sugar will yield roughly 10% Ethanol at which point the yeast stop growing anyway.
Special strains of yeast, like champaine and wine yeast, have stronger cell walls that protect them from the Ethanol -- so they grow longer.

Happy yeast give you long, productive cultures.

The solution is to give yeast less sugar and also supply them with the nutrients they need to grow.
This will give you a long lived culture that produces a consistent amount of CO2, (they are not challenged by toxic conditions at the beginning and end)
Also your yeast mass at the end will be alive and well and able to quickly start growing again when you add more sugar.

The Recipe!
Improvise at will, but here is a good start:
Use 1 cup sugar per 2L H20 (tank water is great or dechlorinated tap -- chlorine, but not ammonia, kill yeast. ) (they like ammonia)
Add 1-2 tsp of a protein drink mix
(optional) Add 1 tsp of ammonium sulfate, otherwise use 1 T mollasses. (or both)
1 tsp baking soda is also nice to keep the pH from crashing (they like it >pH3-4)
Leave yeast from previous mix in the bottom.

Growing yeast this way saves you time (less re-starting) and money on sugar and yeast.
The only real extra cost is the protein mix, but you can use really old/cheap stuff.
The key thing is that it has protein and vitamin/minerals, Anything that has “yeast extract” in it is perfect.
(Even non-fat powdered milk will do the trick, but it will smell funny)

80 Posts
Discussion Starter · #4 ·
Thanks tug and Alex your imformation was really helpful:icon_mrgr I book marked the page so I'll use it when I start up my new tank



Super Moderator
12,131 Posts
That was a very helpful slide presentation. Do you add the whole recipe again when time to renew the co2, or just new sugar and water?
You have to pour out the entire mixture, and add everything all over again.

This is why most people agree DIY CO2 is a big hassle.

322 Posts
it is a hassle. But relatively easy, kind of like a water change. People make it sound more overbearing even though its really 5 minutes worth of work. I will have to try out that recipe until I get my pressurized setup. The reason I don't fully like the DIY method is because it doesn't remain a constant set amount like a pressurized setup. So it kind of throws off the balance a bit. But it gets the job done to an extent for now.

361 Posts
It's only as complicated as you want to make it.

That was a very helpful slide presentation. Do you add the whole recipe again when time to renew the co2, or just new sugar and water?
Save any slurry that's settled on the bottom and when you change the water add the sugar, food/protein (I use spirulina), the whole recipe with a little less yeast possibly. Feeding yeast more then just sugar is what will keep it viable. That slurry should have live yeast culture and will decrease the startup time needed with a new batch. I have also found IME, that a larger surface area then the soda bottles provide will maintain a more stable culture and I use a 4L cube found at a homebrew shoppe.,1223.html I also use champagne yeast from this same site.

DIY is extremely helpful at teaching economy. The levels of CO2 are at best 1-2bps and learning how to use that bubble rate effectively requires an efficient method (reactor/needle wheel) for getting the CO2 to the plants. Even if you go on to use pressurized CO2 (probably cheaper in the long run and much easier to automate when you're away) it's an advantage having learned how to get the most from DIY CO2. The biggest downside to DIY CO2 (fish keeping in general) is trying to get the babysitter to understand the routine. You can't use a timer with DIY to stop it at night.
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