I read that if you are running CO2 24 hours a day you can run an air stone dhen the lights are not on so the CO2 doesn;t get too high. Seems like a waste of CO2 to me so I am going to go the solenoid route.
I have found some 2kg CO2 extinguishers so I would need a regulator and solenoid that has the right fitting. I have read a fire extinguisher uses DIN 477 thread but also read they use a JIS M22-14 so not sure which is correct. I keep coming across chinese stuff though. Is there anywhere recommended in the UK?