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Discussion Starter · #1 ·
I just setup my DIY CO2 system using soda bottles... I have no clue if the CO2 I am inyecting is to much or to little.

I have a 20 gallon tank.

Is there anyway to aproximate the required number of bubbles that need to go in the tank (assuming 100% disolution) to reach an acceptable CO2 level?

I am currently getting a bubble every 3 to 4 seconds.... does that seem right?
 

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I dont know of any standard "bubbles per gallon" rule. I think what you will have to do is measure your KH and pH and use the co2 chart to find out how much co2 your are actually getting. I think a good range is 20-30 ppm. Someone please correct me if I am wrong. You can find the co2 chart here http://www.thekrib.com/Plants/CO2/kh-ph-co2-chart.html

On my diy co2, when fresh, i get a bubble every 2 or 3 seconds.
 

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Discussion Starter · #4 ·
Well I guess my CO2 is on normal range... difference may be due to different mix (I am using about 1.5 litters of water, 3/4 cup of sugar and one tablespoon of yeast.)

How big is your tank?
 

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Discussion Starter · #5 ·
I mean the CO2 production of my DIY CO2 is what was expected... still have to check the water PH to see if it is OK.
 

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Hi. Some of us in Portugal use the following formula:

liters x 13 / 100 = number of bubbles per minute

so in my 120l tank I should have about 15 or 16 bubbles a minute.

(1 gallon = 3.785 liters US or 4.546 liters, British Imperial System)
I don't know how accurate this formula is, though...:roll:

Regards.
 

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Discussion Starter · #7 ·
This comes to about 1 bubble every seconds... so according to this formula I may be adding to much CO2.

I believe however that this is only a guideline... I would presume the number of plants and fish in the tank will play a role in how much CO2 you need and ultimately in how much you need to inject.
 

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Sure. And also if you have a reactor or if you just let the bubbles come out directly from the tube into the water (less effective). Just be careful, use the chart and keep in mind that drastic Ph changes can kill the fish.
Regards.
 

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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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Hi. Giancarlo your article is very helpful, specially for newbies like myself. For instance, I always changed the amount of sugar, thinking it would be more effective (I'll stop doing that). By the way I always use baking soda in my mixture. I was told it doesn't "allow" drastic Ph changes. In fact, values remain stable with baking soda. Have you got any input on this?
Thanks.
Regards.

By the way, I like your final advice. :)
 

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Generally aabout the same amount of baking soda as yeast works well for me. 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. My mixes generally last 3 weeks before replacing. I am also trying something new. Check out my thread in the DIY section "DIY Pressurized CO2". Just use at your own risk. I make no promises or claims. Works well for me though.
 

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Discussion Starter · #14 ·
There are a lot of recepies out there for the mix... I am currently using 3/4 of a cup of sugar, 1 tsp of yeast on roughly 1 liter of water. Does that sound OK?

In regards to adding baking soda to the mix, if I understand correctly the BS will increase the production of CO2, therefore making it necessary to add something to control the preassure on the bottle and the amount of CO2 delivered to the tank. Is this correct or does it only make the reaction last longer withouth increasing the production of CO2 at a given time?
 

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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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Discussion Starter · #16 ·
Giancarlo,

Jello... interesting, could you comment on the specifics of the "recepie" for the mix you use or have used and your personal experiences with it?

Thanks!
~Benicio
 

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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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Discussion Starter · #18 ·
did a search on google and came up with this:

- Add 2 packs of regular jello, not the light stuff, to an empty and clean 2l pop bottle.
- Add boiling water to dissolve the jello
- Add your 1-2 cups of sugar
- Add enough water to fill the bottle to about 1.5l
Store in the fridge overnight to let the jello set.
On the following day:
- Add 1 cup of water and the yeast (1/8 teaspoon) on top of the jello. Attach your bottle as normal."
I am going to try it out. I read somewhere else that one needs one of these bottles for every 30 gallons of water.
 

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Discussion Starter · #20 ·
OK guys... I had not seen the table until today (I did not have a way of measuring PH).... now I measured my PH it is at 7.0 but have no way of measuring my KH... do I need a test kit for that?

I had my water tested yesterday at my LFS.. they said it was to hard and told me to ad salt... does this have anything to do with KH levels?
 
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