You should try to recreate their natural habitat. Research to find out what type of specific corals, sponges and plants the fish have in their open water environment. If a particular fish lives on a coral reef, try to incorporate that into the grand scheme of the aquarium. Stress can be minimized by providing ample opportunities for fish to act normally. Some filters need to be replaced, while other simply need to be cleaned with water. The proper way to change water in a tank is to do it gradually. First unplug any lights and equipment before cleaning the aquarium. Change approximately one third of the water in the aquarium every one to two weeks. Water from the tap should be treated accordingly before adding to the tank and adjusted within two degrees of the aquarium. You may want to allow the tank to run and filter with decorations and any plant life for a few days before introducing the fish. Be sure to clean the decorations and any substrate thoroughly before adding them to the aquarium. Live plants are highly recommended in new aquariums as they will help to generate the good bacteria necessary to reduce the amount of ammonia in the tank. Once you have removed all the gravel, transfer it into a strainer of some sort and run it under hot water. Be sure to mix it up while you are rinsing so that all the sediment and waste is removed. Once the gravel has been cleaned, place it aside. You will not be putting it back in the tank at this time. A fish lover can choose from small cylinder shaped tanks that can double as a coffee table lamp to wall huge wall sized aquariums. While, there are some basic things that will be included in most kits, such as, a filter, some substrate or coral and sometimes lighting, the kits themselves can vary greatly. It may be contaminated, or will at the very least, throw off the temperature and P.H. Allow the fish about two hours to become acclimated before feeding. Only feed an amount that can be consumed in the first two to five minutes. Overfeeding is a common problem in an aquarium. It is important not to overfeed, because excess food will become debris adding to the ammonia levels.