chisme, that's great. Marble chips and lime chips work too.

I didn't like lugging gallon jugs of vinegar. See how long the bubbles last. The egg shells float at first. That's ok. They will eventually sink.

Keep us posted.
Gen Reviewed by Gen on . cheap and easy CO2 I read this in a school science site. To make cheap CO2 use vinegar and egg shells. Crush egg shells and put in a plastic container, then pour vinegar over egg shells. I took a one gallon water jug, drilled a 1/4 inch hole in the top and plugged one end of 1/8 inch black tubing. Then stuck holes along the tubing for the gas to escape. Hang tubing near the top of plants, since gas is heavy. Easy and cheap. Replace vinegar when mixture stops bubbling. Rating: 5