Aquariums allow people the opportunity to view and interact with underwater ecosystems. These ecosystems are found in large bodies of water that naturally filter and circulate fresh water. Aquariums are not capable of this which means that properly maintained filtration systems are absolutely critical for life support. All filtration systems eliminate chemical and physical waste produced by fish and other marine organisms through respiration, excrement, food waste, and natural plant decay.
The nitrogen cycle is the major focus of all aquarium filtration systems. Marine organisms are highly sensitive to the ammonia produced from decomposing waste. The nitrogen cycle is the conversion of ammonia into less harmful nitrates that promote healthy plant growth.
There are three classifications of bacteria present in healthy aquariums. Nitrifying bacteria, Nitrosopumilus maritimus, change the ammonia to nitrite and then to nitrate. This is the major contributor to the nitrogen cycle. Denitrifying bacteria, Thioploca and Thiomargarita, are found in the sediment and convert nitrate into nitrogen. These bacteria help to ensure the nitrate levels do not become elevated in the substrate causing stunted growth in fish, corals and invertebrates. Actinomycetes, Anammox or Saprolegnia, oxidize ammonium into gaseous nitrogen. These bacteria work to decompose cellulose and chitin which are harder to break down. Bio filtration systems harbor colonies of bacteria that start the nitrogen cycle in the aquarium.
Healthy Nitrate Levels
| Freshwater | 15-50ppm |
|---|---|
| Saltwater | below 40ppm |
| Marine Reef | 9-20ppm |