kb/data/en.wikipedia.org/wiki/Aquarium-5.md

title	chunk	source	category	tags	date_saved	instance
Aquarium	6/8	https://en.wikipedia.org/wiki/Aquarium	reference	science, encyclopedia	2026-05-05T09:00:40.028331+00:00	kb-cron

Of primary concern to the aquarist is management of the waste produced by an aquarium's inhabitants. Fish, invertebrates, fungi, and some bacteria excrete nitrogen waste in the form of ammonia (which converts to ammonium, in water) and must then either pass through the nitrogen cycle or be removed by passing through zeolite. Ammonia is also produced through the decomposition of plant and animal matter, including fecal matter and other detritus. Nitrogen waste products become toxic to fish and other aquarium inhabitants at high concentrations. In the wild, the vast amount of water surrounding the fish dilutes ammonia and other waste materials. When fish are put into an aquarium, waste can quickly reach toxic concentrations in the enclosed environment unless the tank is cycled to remove waste.

==== The process ==== A well-balanced tank contains organisms that are able to metabolize the waste products of other aquarium residents, recreating a portion of the nitrogen cycle. Bacteria known as nitrifiers (genus Nitrosomonas) metabolize nitrogen waste. Nitrifying bacteria capture ammonia from the water and metabolize it to produce nitrite. Nitrite is toxic to fish in high concentrations. Another type of bacteria (genus Nitrospira) converts nitrite into nitrate, a less toxic substance. (Nitrobacter bacteria were previously believed to fill this role. While biologically they could theoretically fill the same niche as Nitrospira, it has recently been found that Nitrobacter are not present in detectable levels in established aquaria, while Nitrospira are plentiful.) However, commercial products sold as kits to "jump start" the nitrogen cycle often still contain Nitrobacter. Aquatic plants also eliminate nitrogen waste by metabolizing ammonia and nitrate. When plants metabolize nitrogen compounds, they remove nitrogen from the water by using it to build biomass that decays more slowly than ammonia-driven plankton already dissolved in the water. Some hobbyists also use "anoxic filtration", which relies on bacteria that live in low-oxygen environments.

==== Maintaining the nitrogen cycle ====

The nitrogen cycle in an aquarium is only a portion of the complete cycle: nitrogen must be added to the system (usually through food provided to the tank inhabitants), and nitrates accumulate in the water at the end of the process, or become bound in the biomass of plants. The aquarium keeper must remove water once nitrate concentrations grow, or remove plants which have grown from the nitrates. Hobbyist aquaria often do not have sufficient bacteria populations to adequately denitrify waste. This problem is most often addressed through different filtration solutions: Activated carbon filters absorb nitrogen compounds and other toxins, while biological filters provide a medium designed to enhance bacterial colonization. Activated carbon and other substances, such as ammonia absorbing resins, stop working when their pores fill, so these components have to be replaced regularly. Mechanical solutions, often referred to as protein skimmers. These devices use a combination of high throughput pumps, mechanical agitation (impellers), and air stones to circulate the water column through the system while removing fish and/or coral waste products. These proteins typically form a high density foam that is the then captured in a trap that needs to be periodically cleaned by the aquarist. These systems can also enhance the dissolved oxygen levels in tanks.
New aquaria often have problems associated with the nitrogen cycle due to insufficient beneficial bacteria. Therefore, both fresh water and saltwater systems have to be matured before stocking them with fish or coral. There are three basic approaches to this: the "fishless cycle", the "silent cycle" and "slow growth". This is a common mistake made by beginner hobbyists who are excited to put livestock in their tanks on day one. When a tank is overstocked it can result in excess ammonia build-up, "nitrogen burn" , potentially leading to livestock death. In a fishless cycle, small amounts of ammonia are added to an unpopulated tank to feed the bacteria. During this process, ammonia, nitrite, and nitrate levels are tested to monitor progress. The "silent" cycle is basically nothing more than densely stocking the aquarium with fast-growing aquatic plants and relying on them to consume the nitrogen, allowing the necessary bacterial populations time to develop. According to anecdotal reports, the plants can consume nitrogenous waste so efficiently that ammonia and nitrite level spikes seen in more traditional cycling methods are greatly reduced or disappear. "Slow growth" entails slowly increasing the population of fish over a period of 6 to 8 weeks, giving bacteria colonies time to grow and stabilize with the increase in fish waste. This method is usually done with a small starter population of hardier fish which can survive the ammonia and nitrite spikes, whether they are intended to be permanent residents or to be traded out later for the desired occupants. The largest bacterial populations are found in the filter, where there is high water flow and plentiful surface available for their growth, so effective and efficient filtration is vital. Sometimes, a vigorous cleaning of the filter is enough to seriously disturb the biological balance of an aquarium. Therefore, it is recommended to rinse mechanical filters in an outside bucket of aquarium water to dislodge organic materials that contribute to nitrate problems, while preserving bacteria populations. Another safe practice consists of cleaning only half of the filter media during each service, or using two filters, only one of which is cleaned at a time.

=== Biological load ===