The CO2 in the aquaponics tent was raised to aid the growth of the vegetables. We did it by growing oyster mushrooms on straw in the aquaponics tent. It is actually the growth of the mycelium that produces CO2. Normal outside air is around 400ppm. You can see that the mycelium stopped growing by the end of january. CO2 is back to normal and we should start a new batch of mushrooms.