Freshwater tropical aquariums can be maintained by simply topping up with fresh water.
Most species available are generally bred from fish farms in the far east[2] and Florida[3] where tropical temperatures make the commercial production more viable.
Many marine tropical fish, particularly those of interest to fishkeepers, are those that live among or in close relation to coral reefs.
Hundreds of species can exist in a small area of a healthy reef, many of them hidden or well camouflaged.
Some recreational scuba divers keep lists of fish species they have observed while diving, especially in tropical marine environments.
Coral reefs occupy less than 1% of the surface area of the world oceans,[5] yet they provide a home for 25% of all marine fish species.