Freshwater

Any natural water body, if not marine or brackish, is considered to be freshwater. This includes water trapped in ice sheets, icebergs and glaciers as well as ponds, lakes, rivers, bogs and groundwater. Generally, it is often defined as containing less than 500 ppm dissolved salts (especially sodium salts). Habitats may be described as either lentic systems (contained, still bodies such as lakes) or lotic (moving waters such as streams). Most often, freshwater originates as precipitation from the atmosphere in the form of rain, mist or snow. Freshwater accounts for just 2.5–2.75% of the freshwater on Earth (most of which is locked up in the ice caps). Freshwater lakes contain about 87% of the planet’s liquid surface freshwater. Swamps, believe it or not, account for most of the rest. Only the small remainder flows in rivers (plus 0.04% in the atmosphere). The types that we think of most as aquarists--lakes, rivers, swamps and so on--are extremely varied environments. Because they are more or less closed to other freshwater bodies (i.e. exchange relatively little water), they can differ considerably to one another both biotically and abiotically. Because fresh water bodies are much smaller, they are much more dramatically influenced by climate. Compared to marine habitats, they are much more closely associated with terrestrial habitats and so include more “allochthonous” materials such as wood. All this amounts to a whole lot of diversity. Despite being so much less represented on Earth in terms of volume, freshwater habitats arguable offer a greater number of prospective “biotopes” than saltwater and brackish habitats for aquarists to replicate. In this section, you will explore the many possible biotope aquaria to build and learn of many interesting freshwater species to keep.