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Bubbles per second are really only useful for knowing when there has been a change in CO2 output or to set the bubble rate to where it used to be after having played around with it. It says nothing about your CO2 levels in the tank.

There are too many variables to use bubbles per minute effectively, it's like saying that 10 gallons of gas will get you 100 miles of travel without considering the driving conditions, engine size and weight carried.....

Here are some variables you need to consider:

- If you use a less than perfect method for diffusing CO2, you will need more bubble per minute to maintain the same level of CO2

- CO2 is easily lost due to gas exchange. The amount of gas exchange occuring in your tank will depend mostly on the amount of surface agitation created by your filter's return.

- Temperature of your water will dictate how much dissolved gases it can hold and the ease at which CO2 is dissolved into the water.

- Plant uptake will also play a minimal role in determining how much CO2 il left in the water.

So as you can see, running 10 bubbles per second through an air stone is probably going to give you less CO2 concentration than 1 bubble per second through a powered reactor. Infact in my opinion, controlling surface agitation and diffusion efficiency is the best way to control CO2 levels for DIY setups where CO2 output can not be adjusted.

In conclusion, measure your KH and PH, then use the table to know how much CO2 you have. Once you reach the desired amount, you can note how many bubbles per minute are required for YOUR tank to maintain such level. Should you change the amount of surface agitation or method of diffusing CO2, you will need to re-calculate your required bubbles per minute.

Here's a short article I wrote on DIY CO2, hope it can help
http://www.gpodio.com/diy_co2.asp

This is one of those cases where you "bubble milage" will certainly vary from others...

Hope that helps
Giancarlo Podio
 

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dennis said:
The baking soda seems to slow down the reaction adn it also raises the kH( and thus the pH) of hte mix so the yeast can work longer before it gets to acidic and kills the plants.
I think you meant to say before it kills the yeast.

In general, CO2 production from a DIY setup will be quite high at first and then slowly taper off as the days go by. This makes it hard to maintain a constant CO2 level and people need to resort to tricks such as pushing the micro bubbler (if you use one) deeper and deeper each day to increase the amount of CO2 that is diffused as the rate of production drops. Baking Soda seems to even things out and provide a more stable CO2 production throughout the lifetime of the bottle. A more effective method, yet more work involved, is to use a Jello mixture. The jello makes the sugar available to the yeast a little at a time, therefore maintaining a more stable CO2 output. In this case, the amount of water used is very little so you often need to tip the water out, add some more with some fresh yeast until all the jello is consumed.

Giancarlo Podio
 

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I only used this a couple times to see how it works, in the end however I needed as much CO2 as I could get so I ended up using the traditional method without any kind of stabalizer.

The jello bottle:

- Prepare some jello following regular recipe on the back of the box
- avoid eating it :wink:
- pour the liquid into the bottle and place it in the fridge as the instructions tell you to do
- once it's hardened, activate some yeast in warm water and pour it in the bottle
- The more water you add the better as it will quickly turn to alcohol and spoil the yeast
- when the yeast is dead after a few days, simply tip the water out and add some more water and yeast until all the jello is all consumed, then start all over again

I think it works best for smaller tanks where you don't need all the CO2 produced by a traditional 2lt bottle, it produces less CO2 but it's stable and lasts longer.

Someone posted a much better description once... somewhere, if I find it I'll copy it here.

Hope that helps
Giancarlo Podio
 

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Again, it depends on your efficiency of diffusion and loss. I was able to run my 55 gallon tank on a single bottle, but I had no surface agitation and 100% diffusion rate.

Giancarlo Podio
 

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If you do decide to airate your tank overnight, make sure you test your PH first thing in the morning prior to the turning off the air pump. In many tanks, plant uptake contributes to a small percentage of overall CO2 loss/consumption. Gas exchange actually accounts for most of the CO2 loss in a tank. Therefore, not everyone needs to aerate at night, actually for many, this would cause a bigger PH swing than leaving the CO2 running all the time.

Hope that helps
Giancarlo Podio
 

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I've never required air pumps for O2 levels and feel surface agitation is enough for most setups. The reason why some use pumps during the night is to avoid CO2 levels from becoming too high and possibly becoming dangerous. Although PH in nature will vary from rainfalls and changes in seasons, we are comparing it to a daily change from day to night, this may not be as "healthy" as nature's way of doing things. If your PH changes more than 0.4 between day and night, you could do a little better. If your fish don't seem bothered by your current setup, then don't change anything, they are probably used to it by now.

Due to the high CO2 levels I keep and low surface agitation, I have my CO2 powered diffuser connected to the light timer, this has proven to be the most stable in this tank, if it had more surface agitation I'd probably leave it on 24/7 but wouldn't be able to bring CO2 levels as high as I do now during the day.

It's all about balancing CO2 loss and diffusion rate, plant uptake plays a small part for tanks with moderate surface agitation/gas exchange levels.

Hope that helps
Giancarlo Podio
 
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