I was in a conversation with a plant biologist, who mentioned when looking at a lowland terrium setup, that it should be 'starved' for CO2. Made sense to me, a bunch of plants all in a closed container and photosynthesizing like mad...CO2 concentration should be low. I use a DIY (do-it-yourself) CO2 injector using yeast, sugar, water, a 2L soda bottle and some airline tubing for my planted tropical fish tank...and the plants really grew awesome after I started this. And it's cheap, like $2 per week. So I thought, why not do a similar thing with my 55 gallon lowland terrarium: I could use 2 soda bottles (so twice as much yeast and sugar solution) and bubble the CO2 through a small cup (so I know it's making CO2). What do you all think, so you think the plants will grow better? Anyone else try something like this. BTW, I know they also sell CO2 generators for hydroponic stuff.