The longer it's activated the more chlorine dioxide is released and the more chlorous acid is produced from sodium chlorite and citric acid .
Leave it too long and the chlorine dioxide offgasses more and more.
There are different ways to activate it with different acids but 3 to 10 minutes seems to work with citric or juice
Read Silverfoxes posts if you want to try another method with less acid and weaker 5% sodium chlorite solution