Tips for New Tanks
"New tank syndrome" is the term used for fish mortalities that occur when too many fish have been added to a new aquarium that has not had enough time to establish a good bacterial population. A new aquarium usually takes about 3 to 8 weeks to become established.
The best ways to avoid new tank syndrome are: 1) starting aquariums with hardy fish species; 2) using some biological filtration media from an established aquarium that has not had any major disease problems; and 3) checking ammonia and nitrite levels routinely, especially during the cycling period.
For more information, please read the story Selecting Your First Aquarium.