Two other possibilities:
If room air is high in CO2,the extra volume of air from skimming 200% vs about 160% increase in water volume could increase CO2 density in the tank.
Less density of corals and other photosynthetica animals relative to tank water volume will reduce the relative draw down on CO2 during photosynthesis,assuming the corals are adjusted to the new tank and actively engaged in photosynthesis at the same levels..
If room air is high in CO2,the extra volume of air from skimming 200% vs about 160% increase in water volume could increase CO2 density in the tank.
Less density of corals and other photosynthetica animals relative to tank water volume will reduce the relative draw down on CO2 during photosynthesis,assuming the corals are adjusted to the new tank and actively engaged in photosynthesis at the same levels..
