diy co2 gets weaker and weaker..

[Joetee]

You might try with some different type of yeast like Champaine yeast etc. Try a Brew Shop. It is better for handling a higher alcohol content and would work longer.
Joe

[charpark]

I just conducted a brief (and non-scientific) experiment to test this. In a 1L bottle, I added 2.5 cups of sugar and enough water to reach the shoulder of the bottle (approx. 3.5 cups?) and 1/4 tsp of yeast.

After a couple days, the CO2 generator stopped consistently producing bubbles. However, when I shake the solution, it will produce a huge amount of CO2. Obviously this is an impractical solution.

I drained about 40% of the same CO2 solution, added water to the shoulder to dilute. Then added about 1/4 tsp of yeast. The CO2 is now generating bubbles at a consistent pace, although is likely to not last as long (limited sugar).

It seems that at some point, the alcohol most certainly kills the yeast preventing further sugar digestion. I don't know if there is another reason (e.g., sugar saturation) but from what I've just experienced it does seem that too much sugar can artificially stop the CO2 process before all the sugar is digested.

[Joetee]

2 1/2 cups sugar in a 1 liter bottle... Wow
I used 2 cups in a 2 liter bottle filled to the shoulder with warm water with 1/2 tsp yeast. This worked good for me. I ran 3 bottle all connected together and replaced one every week. This maintained a more consistent C02 level on my 29 gallon. Give it a try.
Joetee

[DaveS]

I have been using the same recipe for almost 10 years now, and I get pretty good production for about a month.

1.89L bottle (generic apple juice bottle)
2 cups of sugar
1/4 tsp yeast
water up to the shoulder of the bottle

One trick I found early on was to boil some water to help dissolving the sugar completely. It takes about 10 seconds to dissolve two cups of sugar in two cups of boiling water. After that, I add about two cups of ice into the pan to get the water back to around room temperature. Transfer to your bottle, and fill the rest of the way with cold tap water. I found having the sugar well dissolved helps quite a bit.

Check for leaks around the check valve as well. I always trim the two ends connected to the check valve at every bottle change. I have found that these sections of the line get worn and loose over time and will start to leak.


Dave

[charpark]

Dave, your post reminded me about a trick to getting tight connections where you unconnect and re-connect your tubing frequently. For example, at your check valve.

The basic premise is to use a new, small section of the tubing stretched over the old tubing. The elasticity and extra thickness prevent the tubing from stretching.

Take some new tubing and cut off a small section (approx. 1/4 inch max). You should now have something like a very short cylinder, almost like an O-ring. Get some needle nose pliers, and insert them into the cylinder, and pull the handles apart, to stretch the tubing piece (reverse of how you normally use pliers). Place this over your original tubing which connects to the check valve. It's a bit tricky, but well worth it.

[Left C]

These are some comments that Nyberg mentioned about using DIY CO2:

"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 champaign 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 H2O (tank water is great or dechlorinated tap -- chlorine kills yeast. ) (they like ammonia)
Add 1-2 tsp of a protein drink mix
(optional) Add 1 tsp of ammonium sulfate, otherwise use 1 T molasses. (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.

Benefits/conclusions
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)"

Here's more info: http://www.aquariacentral.com/forums...t=31965&page=6

[DaveS]

Originally Posted by charpark

Dave, your post reminded me about a trick to getting tight connections where you unconnect and re-connect your tubing frequently. For example, at your check valve.

The basic premise is to use a new, small section of the tubing stretched over the old tubing. The elasticity and extra thickness prevent the tubing from stretching.

Take some new tubing and cut off a small section (approx. 1/4 inch max). You should now have something like a very short cylinder, almost like an O-ring. Get some needle nose pliers, and insert them into the cylinder, and pull the handles apart, to stretch the tubing piece (reverse of how you normally use pliers). Place this over your original tubing which connects to the check valve. It's a bit tricky, but well worth it.

That's a great tip. I think I will try that out on my next bottle change.

Dave

[charpark]

Thanks Left C, I'll take into account your recommendations for my next change out. I hope the recipe will work when halved for a 1L bottle as well. Glad to see we've all learned a bit.