Fishless cycling is a process of creating a biological filter in an aquarium without fish to prevent them from being exposed to toxic levels of ammonia and nitrites. Adding pure ammonia to a fishless tank helps establish the nitrogen cycle, and once the tank is fully recycled, it is ready for fish. Fishless cycling is humane, stress-free, and allows for adding a full batch of fish at once. It also helps maintain a quarantine or hospital tank in case of emergencies.
Fishless cycling is the process of cycling an aquarium or creating a biological filter in a fishless aquarium.
The biological filter, or nitrogen cycle, occurs naturally in the first 4-6 weeks after setting up the tank. Cycling an aquarium is necessary to keep the water free of pollutants and the fish healthy, but as the filter becomes established, the fish are exposed to toxic levels of ammonia and nitrites and often succumb to disease and death. The fishless cycle removes fish from damage by creating the biological filter before the fish are introduced to the aquarium.
Normally, when fish are added to a new aquarium, even if the water is clean, ammonia begins to build up immediately, as the fish release ammonia through respiration and waste. Uneaten food and decaying plants also create ammonia. However, ammonia is required to start the nitrogen cycle, the first step in establishing a biological filter.
In January 1999 Chris Cow, who holds a PhD in organic chemistry, posted an article online about cycling without fish. He had the simple idea of adding ammonia to a fishless tank to get the nitrogen cycle going. This not only saves the fish but also saves the aquarist from stress.
At this point all normal stages of the biological filter can be triggered without concern. Levels of ammonia may rise, followed by toxic levels of nitrite, until eventually both are neutralized. With the tank fully recycled, the ammonia created by the addition of fish will be rapidly converted into harmless nitrate by the established colonies of positive bacteria that make up the biological filter.
Chris Cow’s experiment worked wonderfully and has been used by countless aquarists ever since.
To use the fishless cycle method, simply add 4-5 drops of pure ammonia per 10 gallons of water in a fishless aquarium. Do this once a day until nitrite becomes measurable. At that point reduce to 2-3 drops per 10 liters of water, per day. When nitrite and ammonia are both at zero and nitrate is measurable, the tank is activated. A substantial water change of 25% or more is recommended, then your tank is ready for a full complement of fish.
Only pure ammonia should be used, without detergents or dyes. Ammonia with additives will foam when you shake the bottle. Pure ammonia does not foam.
We recommend a simple dechlorinator/dechloramines while pedaling fishless, rather than products like Prime or AmQuel which sequester the ammonia converting it into non-toxic ammonium. The concern is that the sequestered ammonia may be more difficult for bacteria to process and therefore may slow down the establishment of bacteria. Once the biofilter is established, adding products like Prime and AmQuel is excellent and will not clog the biofilter.
Biofilter bacteria thrive at around 80 degrees Fahrenheit (27 degrees Celsius). If you turn on the aquarium heater while cycling without fish, the aquarium can run in as little as 7-10 days. Be sure to turn off the heater when the nitrogen cycle is complete and allow the water to reach the desired temperature before adding the fish.
The big advantage of fishless cycling is that it is humane and stress-free. Another big plus is that you can add a full batch of fish in one go, because the biofilter is fully stabilized. This is especially significant when keeping territorial fish that are best added all at once.
Other benefits include maintaining a quarantine or hospital tank in case of an emergency by simply adding a drop of ammonia to it each day to simulate the presence of a fish.
Any aquarist who has gone through the difficulty of cycling an aquarium with fish will surely appreciate the fishless cycling method!