This toxin is chemically changed to nitrite, and then to nitrate. Ammonia and nitrite are very toxic in fresh and marine aquariums, and should not be present in any measurable quantity, at any time. Nitrates are not nearly as harmful, but do cause algal growth when in high concentration. Unfortunately, nitrates are not removed by this process. You must use a denitrifier to remove them, or perform extensive and regular water changes.
Biological filtration is absolutely necessary in any aquatic ecosystem.
Although they work fine on smaller freshwater aquariums, they fall short on larger systems and on reef tanks in general. Biological Canisters such as the Ocean Clear are designed to house the aerobic bacteria necessary to undergo biological filtration. Water is pumped through the vessel by a pump or powerhead, and is processed and returned to the tank where it is then free from ammonia and nitrite. These filters house 'biological media' in which bacteria are drawn to. They are sustained by running water that is pumped over the media.