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Old 03-16-2004, 10:26 AM   #1 (permalink)
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Default How many CO2 bubbles per gallon of water?

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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Old 03-16-2004, 01:13 PM   #2 (permalink)
 
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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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Old 03-16-2004, 01:49 PM   #3 (permalink)
 
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Right on Kevin,

It would also be interesting to use the chart to see how much CO2 is in the water before injection. It only may be a couple of ppm. Even if you got it to 15 ppm it probably would be helpful.

Steve
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Old 03-16-2004, 01:50 PM   #4 (permalink)
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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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Old 03-16-2004, 01:56 PM   #5 (permalink)
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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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Old 03-16-2004, 06:29 PM   #6 (permalink)
 
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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...

Regards.
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Old 03-16-2004, 06:38 PM   #7 (permalink)
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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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Old 03-16-2004, 06:46 PM   #8 (permalink)
 
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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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Old 03-17-2004, 09:27 AM   #9 (permalink)
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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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Old 03-17-2004, 12:31 PM   #10 (permalink)
 
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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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