Deciding whether to purchase a saltwater aquarium or a freshwater aquarium has a lot to do with how you feel about the fish. The fish from the ocean are generally more exotic and beautiful, but also much more expensive, than freshwater fish. They also have other differences that can help with the decision between the two types.
Freshwater fish use gills that filter water as they breathe. The bodily fluids remain inside the fish. Saltwater fish, on the other hand, lose a good deal of body fluids into the water through osmosis. Thus the saltwater fish has to consume large amounts of salt water to maintain homeostasis.
Freshwater fish can live in a variety of habitats, depending on the type of fish. Some can dwell in comfortably cool water while others can thrive in cold water. This is because there are fish that come from tropical areas and those that stem from the Antarctic and Arctic.
For many saltwater fish, coral reefs, seagrass beds, salt ponds and mangroves are the natural habitats. In fish tanks, saltwater fish do well with some life plants like coral, anemones, and seaweed varieties. Live rock helps to keep the water clean.
Freshwater fish include such varieties as cichlids, catfish, platies, salmon, whitefish, mooneye, and char. Some of the better known saltwater fish include cod, marlin, snapper, sharks, bluefish, eels, and flounder. While cost is definitely a factor, it is usually preference that wins out, when someone purchases a saltwater aquarium. A saltwater tank can be a beautiful focal point in any room.