I accidentally killed off all of the fauna in a tank last night, lost all of my breeding danios, some new otos that were doing quite well, and a bunch of snails and shrimp. I was ramping up my CO2 but fell asleep before I had it dialed in.

Totally my fault, and I know what I did wrong, but it got me thinking:
What CO2 level could/should be run in a tank without animals?
In my specific case, this tank is a new "moss scape" that has just started to really grow (mostly Singapore and a little Java). I have some vals and hair grass as well, but the moss is supposed to eventually cover about 80% of the tank. How high could I keep my CO2 if I never add animals to this tank again? Would overdriving the CO2 accelerate moss growth, or would a system balanced out with fauna see better growth? I auto dose ferts daily and have modular CFL lighting that I can up/down as needed (sky's the limit). I just can't figure out the right words to Google, lol.
Andrew