In January 1999 Chris Cow who holds a Ph.D. in organic chemistry, posted a paper online regarding fishless cycling. He got the idea to add ammonia to a fishless aquarium in order to get the nitrogen cycle going. This not only saves fish, but it saves the aquarist from stress as well.

Fishless cycling is when you artifically start the biological filter (nitrogen cycle) process in an aquarium without fish.

Typically the nitrogen cycle takes between 4-6 weeks to complete. The nitrogen cycle allows "good" bacteria to establish thus breaking down the fish wastes. Cycling a tank is necessary to keep the water free of pollutants and the fish healthy, but while the filter is establishing itself, fish are exposed to toxic levels of ammonia and nitrite and often succumb to disease and death. Fishless cycling removes fish from harm by establishing the biological filter before fish are introduced to the aquarium.

At this point all of the normal phases of the biological filter can be triggered without worry. Ammonia levels can soar, followed by toxic levels of nitrite, until, finally, both become neutralized. With the tank fully cycled any ammonia created by adding fish will now quickly be converted to harmless nitrate by the established colonies of positive bacteria that make up the biological filter.

Biofilter bacteria thrives at about 80 degrees Fahrenheit. If you turn up your tank's heater while cycling fishless, the tank can cycle in as little as 7-10 days. Be sure to turn the heater back down when the nitrogen cycle is complete, and allow the water time to reach the desired temperature before adding fish.

The great advantage of fishless cycling is that it is humane and stress-free. Another great advantage is that you can add a full complement of fish at once, because the biofilter is fully established. This is especially significant when keeping territorial fish that are better added all at once.

Taken in part from Wisegeek.com