The vast majority of freshwater fish commonly kept in aquariums are warm water or Tropical. There are also or Moderate species as well as species that require temperatures higher than Tropical. To understand this division better, it helps to understand where freshwater fish are found. The Tropical Zone is the area immediately on both sides of the equator between the Tropic of Cancer (longitude 23.5° north), and the Tropic of Capricorn (longitude 23.5° south). The Moderate or Temperate zones are then found between those Tropic lines and the Arctic and Antarctic Circle lines (longitudes 66.5° north and south respectively). It is important to note, however, that there are pockets of temperate climates due to altitude within the Tropical Zone, but species found in these zones are extremely uncommon in the aquarium trade.
Aquarium Temperature Management: Prevent a Warm Water Disaster
Some fish species like brook trout cannot live with much salt in the water, other fish, such as tuna and, need salt, and some, such as striped bass, can live in salt or freshwater. Fish also need a certain amount of oxygen in the water. Species such as carp can live on less oxygen than trout. Living plants add oxygen to the water as does moving water tumbling over rocks. Decomposing plants and animals use oxygen from the water and many kinds of pollution also reduce oxygen levels. Thermal pollution may also be a problem as warmer water cannot hold as much oxygen as cold water.
have very cool consistent temperatures, it will suffer in warm water.
This important reference book provides standard sampling methods recommended by the American Fisheries Society for assessing and monitoring freshwater fish populations in North America. Methods apply to ponds, reservoirs, natural lakes, and streams and rivers containing cold and warmwater fishes. Range-wide and eco-regional averages for indices of abundance, population structure, and condition for individual species are supplied to facilitate comparisons of standard data among populations. Provides information on converting nonstandard to standard data, statistical and database procedures for analyzing and storing standard data, and methods to prevent transfer of invasive species while sampling.
10 Best Freshwater Fish For Beginners - ClubFauna