Hey people, I'm working up my idea for mini underwater bio domes, and I could use some advice now...I can not decide on how to create the oxygen cycle. I know I need animals to take in Oxygen and produce carbon dioxide, and I know they need a sustainable, renewable food source as well, but I don't want them attacking or eating the cannabis I plan to use as the tree-role in this experiment. So basically what I need, is suggestions on animals that could be used.
Keep in mind, these bio domes are being designed to be relatively small, say around one cubic meter.