Aquarium water conditions classification

Aquariums are first distinguished primarily by the salinity of the water. Saltwater aquariums have the highest proportion of dissolved salt in water. Living conditions in saltwater aquariums are simulated as they occur in the oceans. The salinity is 3.4 percent.

In freshwater aquariums, the proportion of salt in water is less than 0.6 percent. These mimic the conditions of life in a lake or river. This type of aquarium is the most widely used.

Brackish water aquariums, however, are a relatively uncommon aquarium. They form under the conditions of the estuaries of large rivers and coastal mangroves. The salinity is between the values of salt and freshwater aquariums.

Many tropical waters (needed when keeping tropical animals in the aquarium) have low-salt, and very soft water. Names such as the Amazon basin or black water aquarium indicate freshwater aquariums that simulate these conditions, while being maintained in a black pool of water. However, there are species from different backgrounds who call for this condition that are kept deliberately in an Amazon Basin, as opposed to keeping only those plants, fish and invertebrates which are originally distributed from the Amazon area.

Malawi basins, or so-called East African fish aquariums, usually host the East African lakes that have a much higher salinity. Aquariums for domestic cold-water fish are also often harsher than those for warm-water, tropical fish; the term “hard-water basins” however, is unusual.

A specific type of aquarium is the so-called backwater aquarium. Here regular, partial water changes are dispensed with and only evaporated water from rainwater or distilled water is used. It is necessary to have only a very small fish population so that filters and plants have the ability to convert the resulting metabolic products. This type of aquarium is a form that is controversial.