You probably know about end-of-tank dump

a single stage regulator is an
enormous risk to overdose those fish when you get close to the end of the CO2 in the tank




What this means is that, by the very nature of a single stage regulator, unless you disconnect and refill the CO2 bottle before it gets to the end of pressure, the regulator will allow the remaining CO2 to rush out and poison your livestock.
I don't think you mentioned what you are using to diffuse your CO2

Protecting your livestock from end-of-tank dump is actually the number one use case for a Yugang CO2 reactor that is designed and sized specifically to match the size of your tank

Contents:
Benefits of Yugang reactor
Calculate the reactor dimensions
Overflow mode, regulator mode, pH/CO2 controller
Overflow mode, step by step instruction
Regulator mode, pH/CO2 controller mode, step by...
It can be a helpful stopgap until you're ready to go to a dual stage regulator