Hello,

We are doing a science project testing to see if it’s possible to grow more algae with supplemental co2 (brewer’s yeast, sugar and plant food), than without. Initially (1st 3 weeks) looked promising. Then something remarkable happened. The control bottle (no added co2) grew more algae than the supplemental co2 bottle. A complete reversal at about week 4. . We are trying to figure out why this would occur. Could you give some intel?

Thanks,
Roman Nasif
7th grader at Khalsa Montessori School
Tucson, AZ

You would really need to know CO2 concentrations. Even with "No added" CO2 you do have some in the ambient air. The concentration of added CO@ may inhibit growth if too much exists. Read this:

https://scienceblog.com/522/climate-surprise-high-co2-levels-can-retard-plant-growth/