Domesticated tropical fish as compared to their cousins in the wild are usually more attractive and colourful. This is due to selective breeding done by aquarist with some other fish species. If you still remember the lessons taught in Biology class, another reason why tropical fish in the wild does not exhibit attractive colours is because of "Natural Selection". Fish with genes that determine bright colours will usually more prone to be spotted by predators, thus leaving the wild fish with dull colours better chance of survival.
There are actually thousands of species of fresh water tropical fish that has been categorized and identified by scientists. Most of these fish are actually found in the Amazon river and it's known to be numbering more than 3000 species! The largest fresh water tropical fish, Arapaima, also belongs to this river and are believed to be the largest in the world, with length of up to 15ft/4m while weighing 440lbs/200kg. Other better known tropical fresh water fish is the piranha which is the most dangerous fish ever known and are also domesticated although it has been banned by certain countries. Other fish like the Neon Tetra, Swordtail and Discus are also examples of fresh water tropical fish which are kept as aquarium fish and originated from the rivers of the Amazon.
Pollution and changes in the environment are threatening existence of fresh water tropical fish and scientists have predicted that these numbers will dwindle and eventually become extinct in the next few decades or so. Therefore, don't be surprised to learn that in the future, fresh water tropical fish that we will ever get to see, are the ones left remaining in home aquarium.
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