DIY co2 bubble rate

vato

vato

AC Members
Apr 17, 2001
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British Columbia, Canada
I completed my first DIY co2 injection system today. It is a very basic setup with one, 2 liter bottle. I put in it a mixture composedof: 3/4 cup sugar, 1 teaspoon yeast, a pinch of baking soda, and 6 cups water. My question is how can I control the flow rate? As it was I was recieving about 2 bubbles per second, so I put a hose clamp on it to slightly restrict the flow. I adjusted the rate to a bubble every three seconds. But as soon as, I released it a stampede of co2 raced to the surface. So how can I adjust the rate so that I am receiving an appropriate amount of carbon dioxide? I am assuming that if I use the hose clamp that the pressure in the bottle will contniue to grow until the bottle itself explodes. Thank you in advance for all the help.
 
You've found the biggest flaw in DIY CO2 -- there's no way to regulate the flow rate other than experimenting with the mixture. You're correct that if you use a hose clamp, you'll have an exploded bottle and a smelly room.

A new batch of CO2 tends to spike initially -- keep track of the bubble rate and KH/pH, and I bet you'll find that production levels off soon.
 
That recipe seems kin da of..odd. Most of the recipes ive read about and tried have usually been around 2 cups of sugar and 1/4 to 1/2 tsp of yeast and sometimes a pinch of baking soda, and then some instructions on the water temp and when to shake it up ect.

That flow of Co2 is very high, which probably is too much. The only thing i can think of is try a different recipe, search 'diy co2' on google and try the recipes that the first 2 or 3 links give. I did the recipe that the first link gave (http://www.thekrib.com/Plants/CO2/co2-narten.html)

I used a standard 2l bottle with tubing, and no check valve and by just drilling a hole, sticking the tubing into the bottle 1" max, sealing it very well, making sure the glue was dry, and following the directions of that link very closly. It took maybe 2 days for it to get up to its fastest bubbles per minute rate. Now it does a bubble maybe every 15 to 18 seconds. Which i think is a good healthy rate, and for doing SO little. Its probably the cheapest way you could do a DIY co2.

I dont know if this helped, but it's the best info i could offer.

~ MyShrimpDied
 
It's impossible to say whether 2 bps is too much or too little, really. It depends on the tank. The only reliable method of determining CO2 concentration is to use the pH-KH-CO2 formula, and even that can be thrown off by phosphates and excess organics in the water. It's going to take steady observation to determine what works best for your tank. Take a look at this good thread in the plants forum for more in-depth info.

3/4 cups sugar sounds pretty good, actually. Yeast guru Tarah Nyberg has said that most DIY CO2 recipes use too much sugar, creating toxic conditions for the yeast. Check out her informative PowerPoint presentation (first item under "Resources").

HTH.

-John
 
Here's the thing, I've, for years, recommended(I work in a LFS) people to use a DIY co2 system as a cost effective way to have a small, planted tank. But I have never run this system myself! Kind of silly I know. MyShrimp, I have gone through a countless number of recipes and there are a few that reflect each other but they are almost as varied as the sites that I find them on. I used mostly the same system as you but with a check valve. (I didn't want to chance it, I did before with my air pumps, It took 8 years for anything to happen, but once it did, I decided it's worth the extra couple bucks to do it this way.) I have been adjusting the flow by opening the lid of the reactor ever so slightly, and it seems to help a little. Do you think that a couple bubbles per second are a problem if they are not diffused in any way?
 
It may be, I remember someone posting on here saying that the were getting 1 bubble per second and saying that it was too much. I think the correct level you want is 20ppm of Co2 in your tank. I would just experiement i guess.

~ MyShrimpDied
 
I'll say it again -- there is no such thing as a universal bubbles-per-second that is "too much." You've got to measure your pH and KH to get any idea of what's going on as far as CO2 concentration. Two bps may be fine for your tank -- you won't know until you do the proper tests.

If you don't diffuse your CO2, you will get little to no benefit, no matter what the bps may be.
 
Originally posted by MyShrimpDied
Does running the tubing into your filter intake count as diffusing it?
Click to expand...

Yup! That does a pretty good job of it, too.

Anything that keeps all or some of the CO2 bubble from entering the atmosphere (i.e., leaving the water) qualifies as diffusion.

Edit: I should clarify this, actually. Typically "diffuser" is used to describe something that makes the bubbles smaller, whereas a "reactor" brings the water to the CO2 bubbles, dissolving the CO2 into the water. Running the bubbles into your filter intake essentially creates a reactor.

Using a reactor still qualifies as "diffusion" since you are spreading a concentrated form of CO2 into the water, but I thought I should clarify things to keep the terminology straight.
 
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What I did was put a T connector on the tubing. Then run a short piece of tubing in the extra outlet. Put a flow control on that tubing and adjust so that you are venting a little Co2 into the air. Then you can adjust again more or less to get where you want to be. You can also put the end of the tubing in a glass of water, so you can actually count the bubbles you are venting.
It takes some fiddling around and some patience, but it works.
 
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