CO2

[BigDaddy]

I'm not sure if you are agreeing with me or not.   :lol:

Essentially, we have two volumes of yeast in comparatively the same amount of solution (an almost filled 2 litre bottle).

Solution with volume X of yeast will produce less alcohol and thus be better able to consume sugars longer than the same solution of 4X, where alcohol concentrations will increase in solution significantly faster.

In other words, I believe the popular opinion is that most of our yeast generators stop production because of alcohol levels, and not from sedimentation.

[jabber]

What I am trying to say is that both will produce an equal volume of CO2.

Solution A starts with volume 1X of yeast. Solution B starts with 4X yeast.  Solution B starts to ferment and produce CO2 instantly (*not realisitic just used for demonstration).  While solution A does not produce CO2 until the yeast has multiplied to the 4X level at wich point solution A starts to produce CO2 at the same rate as B.  Frome now on A and B consume the fermetable sugars at the same rate. So, solution B will "last" longer only because it started producing CO2 later.  The same volume of CO2 will be produced by both.

I just mixed up a batch using 1.5 Liters water and 1 cup sugar and got a specific gravity reading of ~1.064 which equates to ~8.5% alcohol at 100% fermentation.  Table sugar is not very fermentable and it is probable that all the fermenatable sugars get used up before the yeast dies (at this concentration).

[BigDaddy]

Why wouldn't solution 4x have to go through the same lag and growth phase as 1x?

Additionally, while the total volume of CO2 dispersed would be the same, is it not a time release issue?  Volume 1x generates a CO2 rate more manageable to the aquarist, while volume 4x, as you have pointed out, starts fermenting much sooner (and therefore providing too much CO2 out of the gate).

[jabber]

Solution 4x has to go through some growth as well (that's why I put the disclaimer of not realistic) just not as much growth because it started with a larger pitching rate.

Ignoring the lag phase, lets concentrate on the growth phase:

II)  The second phase is the accelerating growth phase during which yeast cells start to grow and divide.  Signs of fermentation will also become apparent.  The yeast begin storing sugar in the form of glycogen for later use.

III)  The third phase is the exponential phase where yeast reproduction and metabolism is in high gear.  Cells are dividing every 90 - 180 minutes and fermentation begins.  During this time the number of yeast cells may increase as much as 1000-fold (or 3.0 logs) within 24 hours.  The extent to which the cells divide is dictated primarily by the pitching rate.   If appropriate pitching rates are used, the yeast are pitched at high concentrations (5-15 million yeast cells per ml) and undergo approximately 3 generations (23- or an 8-fold increase in cell number) to yield 80-100 million cells per ml.   100 million cells per ml is about the maximal concentration of yeast attainable in fermenting wort [Wort, for those not familiar with brewing beer, is the unfermented sugar solution i.e. the almost the same as what is in the CO2 reactor.]

IV)  The fourth phase is the decelerating growth which should occur 12-24 hours after pitching.  At this time the oxygen is fully depleted and fermentation and CO2 production is taking over.  Fermenting wort should be in high krausen.   Heat is being generated and there should be rapid CO2 evolution (bubbling).          

So, while solution 1X is still growing (phase 3) solution 4X has reached phase 4 and started to really generate CO2.   Since both 1X and 4X reach the same conentration of yeast which are producing the same amount of CO2 there will not be "too much CO2 out of the gate".

[BigDaddy]

And again, I do not argue with the total volume of CO2 being produced, but rather the amounts produced over the total time frame.

There is evidence that yeast mixtures last longer (for our purpose of CO2 production, not for fermentation in general) if you decrease the amount of yeast, and conversely last shorter periods if more yeast is used. Lower yeast also means less CO2 produced per minute, but produce more consistantly over time. Higher yeast levels will cause an initial higher burst of CO2 production with a gradually declining production over time.

So again, I do not argue that the total volume of CO2 produced won't be very close.  Rather, since aquarists are concerned with how many bubbles per minute the generator is producing, less is more when it comes to DIY CO2 generators.  Less yeast means a slower, but more consistent, bubble per minute rate.  More yeast has a significantly higher bubble per minute rate at the outset, which gradually tapers off.

Since our goal is to maintain relatively equal concentrations of CO2 from day to day, a more consistent number of bubbles per minute is more desirable.

[Nelson]

My head's starting to hurt :shock:

[gator]

I agree, my head hurts too.  Why not just buy a 10 lb C02 bottle and be done with it?

[Toss]

I agree with both of you ...jabber and BigDaddy. I started with 1 teaspoon full. The bubbles started very quick, and the rate was quiet high and slowing down after. I reduced it by half, and it takes longer to starts producing bubbles. The rate is also slower. I am not an expert, so it took me a few tries with different recipe until I am happy with the result. Good luck Iceman.

[BigDaddy]

PS - I used to be a DIY guy... but I've gone pressurized and I'm not going back!

[gvv]

My head's starting to hurt :shock:

And I liked this it! :lol:   Reminds me of days when I was in a science...

[Nelson]

PS - I used to be a DIY guy... but I've gone pressurized and I'm not going back!

It's absolutely the only way to go.  It's an investment at the outset but it's worth every penny not to be concerned about continually recharging a DIY setup.  The conveniece of adjusting for a constant flow is also great.

[Iceman]

So how much does it cost to set up a pressurized system for a forty gallon tank?

[BigDaddy]

Pressurized is not tank dependant... a pressurized setup will work just as well on a 10 gallon as it will on a 200 gallon.

If you bought everything brand new (tank, regulator, solenoid, bubble counter) - it'll run you 340 bones from a local store that carries the stuff.  Same setup without the solenoid would be 260.  If you are lucky, you might be able to find a used CO2 tank, although the guys where I get mine filled say they are getting harder to come by these days for some reason...

Then you also have to look at how you are planning to dissolve the CO2 into the water column (a DIY inline reactor will cost you a few bucks in PVC... commercial products will cost significantly more).

[Iceman]

When you say local store, do you mean pet shops?

[BigDaddy]

No... aquaria canada sells co2 equipment.  They use CO2 in calcium reactors for saltwater.

You can get the stuff online too.... but I just used aquaria canada's pricing 'cause it was easy to find.