If a marine fish is placed in a fresh water aquarium, it will be difficult for it to survive. For aquatic organism the quality of water (chemical composition, pH, salt concentration) is an important factor for it’s survival. Many freshwater animals cannot live for long in sea water and vice versa because of the osmotic problems. The bodies of the marine fish are adapted to survive in high salt concentrations. In fresh water conditions, due to the presence of high water condition outside their body they are unable to regulate the water entering inside their body. This results in the swelling up of the body and eventually leading to the death of the marine fish.