Symptomatic, struggling systems allow opportunity for obvious noticeable changes.  DOWN JOHN reverses and revives struggling systems but was also designed to maintain healthy apparent asymptomatic ones.  DOWN JOHN restores balance to the internal science make-up of your tank, lines and drain field.  A healthy system receiving treatment will show signs of internal improvement in digestion levels but may be less likely to display overt observable changes outside the tank. No news is good news!