Use Dr Tim's One & Only when setting up a new tank, after a water change, cleaning your filter, when adding new fish and after a disease treatment to control ammonia and nitrite.
The key to setting up a successful aquarium is to quickly convert fish waste into a non-toxic form. This is done by nitrifying bacteria. Under normal conditions it can take 30 to 45 days for this bacteria to become naturally established in a newly set-up aquarium. Unfortunately, during this time period, ammonia and nitrite can increase to levels toxic to fish - a process called New Tank Syndrome. For years, it was assumed that two particular species of nitrifying bacteria were responsible for this process but original scientific research by Dr. Timothy Hovanec showed this not to be the case. This is one reason why nitrification products have failed to work in the past.