Welding gas

The other is far more $$, and a lot harder for anyone to get/refill for use.
If you raise the turbulance for the tank, then you have less nighttime issues with low O2.

You waste more CO2 during the day, but that's easy and cheap to add more of.

Then you do not need an airstone, nor O2.
But in over stocked systems, it's advisible.

Regards,
Tom Barr