we dont! most people lower co2 levels before adding fauna then adjust back up over a few days once their settled.
if you are going to add them, add them before co2 comes on and your around to take emergency action if levels are too high
Yeah was going to wait until I am at home all day so sunday morning might be a good idea .... hopefully I can find my test kit in the meantime
PS I know not to add to the tank when there is high levels of Co2 going in, I just meant in general terms as in having a high tech tank