Freshwater aquarium fishes always look beautiful. Freshwater aquarium keeps the fishes healthy, as like lived in their natural environment. Natural world toxic gas is harmful to fishes. So keep process of changing the tank water routinely to reduce the ammonia in the water. PH, the index of hydrogen ion concentration, is one of the most important factors in determining aquarium productivity. Water pH 4.5 and below has been observed to kill aquarium fishes. Coral skeletons, shells, and other calcium containing objects of decoration can be avoided in fresh water.