29 Gallon Tank CO2 confusion


Okay well I'm kinda confused with this whole CO2 thing that I have added this past week so here goes...

I have a 29 gallon planted aquarium. It has high light (2x 24 watt t5 high output bulbs). I decided to add CO2 to my tank via DIY methods due to an algae spike I got after upgrading my light (mostly brown and hair algae). Currently I am running 2x 2 liter bottles with 2 cups sugar 1 tsp baking soda and 1/2 tsp yeast a piece. I put a gang valve before my drop counter to allow me to adjust how much CO2 I'm getting. I have about 1 bubble going into the tank every 2 seconds. I am diffusing the CO2 by running the tubing into the intake of my powerhead and am angling it down at 45 degrees. I get very tiny bubbles which I know is good. Currently the only aeration my tank has comes from the filter output.

I know plants provide Oxygen during the day and absorb CO2. At night they absorb Oxygen. Right now I have no materials to measure the amount of CO2 in my tank via a drop checker or a 4dkh solution to compare with charts (I've read those solutions are hard to make without lab materials). I am hoping to get something soon. I know counting bubbles is not very accurate with DIY but is there any way I can get a rough approximation if 1 bubble every 2 seconds is good or do I need to turn it up or down? I'm thinking about adding an airstone to my tank and only running it at night. If I do this can I leave the CO2 going while I aerate the water? I know this is a lot to ask at once I just need a lot of advice...lol.

Thanks for any help!

Nate McFin

Dont try to shut the Co2 off. If you shut it off the bottle will likely explode. You can run o2 at night and it will be a safety measure for you, but with 1 bubble every 2 seconds you are a long way from any sort of danger zone.


In order to get enough CO2 into your tank I'd think you need 1-2 bubbles per second.

Do you have a liquid pH test kit? If so, you can use it to estimate how much Co2 is being absorbed. You should know your tank's normal pH. To drop the pH 1 degree takes 30 PPM CO2.

Definitely do not try to stop the gas production from the soda bottles. As Nate already stated, you will end up with those bottles exploding.


Ya I figured as much I was never going to try to shut the Co2 off, just oxygenate at night. I picked up a drop checker yesterday. It's a Fluval Co2 indicator. I've got close to a bubble a second now and it looks like it is right in the green where it should be. looks like a light green but I don't think I would have too much going in my tank. I'll leave it set up like this for awhile see how things go. I just get nervous adding something to my tank that I can't measure, glad I was able to find a drop checker with a pre-made solution. I'm amazed at how efficient my system is for a DIY.

I have a liquid API Master Kit I use and I did notice probably close to a 1 degree drop in my aquarium's pH.


Watch your ph change closely. More than 1 degree change may start to affect your fish. Many have lost fish with too much CO2 being absorbed.

Something else you may want to test is your kH and gH levels. Knowing these levels will also affect your pH. The lower your kH the more unstable your pH. And, it could suddenly crash.

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