Adding co² is sheer bullshit.. the only way it could be good for something is when you don't have the oppurtunity to ventilate or add CO² tabs too the water for more nodes.
britewire Reviewed by britewire 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