ks and sand from an established aquarium. The bacteria that live in these materials will quickly multiply and spread throughout the new aquarium. This bacteria makes up a biological filter that removes waste byproducts in what is known as the nitrogen cycle. The nitrogen cycle is basically a three-step conversion of harmful products in the tank to products that are somewhat beneficial. The first step in the nitrogen cycle is to convert ammonia in the tank into nitrites. Just as trees and plants ingest carbon dioxide to produce oxygen, animals that consume protein for food produce ammonia as waste products. Ammonia in a marine reef aquarium is extremely toxic to the inhabitants if they reach levels of .0002 grams per liter of water (Shimek 63). Levels even lower than that will cause stress to the inhabitants, which makes them susceptible to diseases. Some of the bacteria that live within the filter media and throughout the aquarium digest ammonia as food and expel nitrites (Madison 41). Nitrites are not as toxic as ammonia, however they are still toxic to the inhabitants. So the second step in the nitrogen cycle is to get rid of the nitrites. Other bacteria within the aquarium remove nitrites in the same way that the ammonia is removed (Madison 42). This second form of bacteria will consume the nitrites as food, and expel nitrates back into the tank. The last step of the nitrogen cycle is to rid the aquarium of nitrates. Although fish and invertebrates can stand a higher level of this chemical, it is something the hobbyist must watch closely. There are bacteria that will consume the nitrates, but at a much slower rate than ammonia or nitrites are consumed (Madison 42). This allows some forms of algae to feed on the remaining nitrates. Although some algae growth in a marine aquarium is beneficial, an algae bloom can occur if nitrate levels grow too high. The best way to control nitrates within a marine aquariu...
