I have stuck to freshwater instead of saltwater aquariums because I am concerned with the destruction of natural habitat and fish species by the irresponsible harvesting of fish, inverts, and coral/reef from the wild. While most frshwater tropical fish species are captive bred, over 90% of saltwater are wild-caught. Even when I buy the freshwater fish, I try to look for fish that are locally bred. Unfortunately, the aquarium hobbyists are responsible for significant habitat destruction and threaten certain species' existence in the wild. FOr more info do a google search or see:
http://www.uwsp.edu/geo/courses/geog100/CoralReef-Consume.htm
"Approximately one million marine aquariums currently exist in the United States, constituting two-thirds of the world total. The approximate retail value of annual sales of living marine organisms totals US$200,000,000. Additional sales of non-living products for establishing and maintaining home marine aquariums totals US$300,000,000. Thus, American hobbyists spend half a billion dollars annually in pursuit of their interest in coral reef denizens.
Over 90 percent of all live marine aquarium organisms are collected from coral reefs, with the remainder coming from various types of captive propagation. While Florida and Hawaii are significant sources of specimens, most, including all stony corals, come from Indonesia, the Philippines, and elsewhere in the Indo-Pacific. A small percentage of the trade originates in Africa and the Middle East. "
"Such destruction of coral reef ecosystems will continue-- perhaps even worsen-- as long as (1) reef species continue to be commodities for profit and highly valued by many collectors (see prices at commercial sites listed below) and (2) world trade of reef species remains poorly regulated and virtually unenforced. "
"1 in 10 fish which are caught even live for 3 months. Of those, probably only another 10% live for a year or so longer. The primary reason for most fish dying within the first 3 months is improper collecting and shipping methods. The primary reason the surviving fish do not live longer than a year is due to lack of proper care by the hobbyist"