# Maintaining a 40% CO₂ aqueous environment?

I wish to grow algae in a 40% $\ce{CO2}$ (water under air with 40% $\ce{CO2}$ content) aqueous environment.

Simple DIY methods are available, but they are generally unreliable (For more info on DIY read here) because they rely on a pH/KH chart.

Atmospheric $\ce{CO2}$ levels are measured based on IR absorbency. However, such measurements are difficult and "complicated by the temperature signal generated by carbon dioxide as well as by the signatures of ozone and water vapor."

Is there a reliable way to measure the $\ce{CO2}$ concentration that is relatively inexpensive (under $1,000)? Is the drop checker method reliable? • ergh. Please, clarify: do you need 40 weight % water solution of$CO_2$, water under air with 40% of$CO_2$with atmospheric pressure or something else? – permeakra Sep 13 '12 at 14:06 • there are companies, providing industrial-level solutions. Home-brew solution should include arduino board,$CO_2$gas cylinder,$CO_2\$ sensor and electronically controlled valve. – permeakra Sep 16 '12 at 8:31
• Unfortunately, I feel that the answer you desire could be a hair too involved to set up a home-made system which appears to be your desire in this case. I can guarantee you a wide family of correct answers to your problem await via a quick google search, but, and please understand that I only wish to help here, I fear that two sentences and a bounty are not a significant step towards what is likely an in-depth solution of the many out there. I wish you the best of luck however, and hope you revise your question soon. – Leonardo Sep 16 '12 at 23:50