This is perhaps one of the most interesting and enjoyable aspects of setting up an aquarium. The decorations should be chosen in consideration of the species of plants and fish that will be kept. Plants require room to grow and their locations should take into account their full size and light requirements. The value of live plants in the aquarium goes well beyond that of decoration, as they are major contributors to water quality and benefit fish in many ways. For species of fish that cannot be housed with live plants, the use of plastic plants represents an excellent solution. Conducting a little research into the different themes of aquariums will provide a logical first step in setting up a successful aquarium. Some of the possible aquarium types and suggested decorations are shown in the links above.