Fish should be made to feel as comfortable as possible in their new home. 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. During the eighth week, you can add Aquacultured Coral such as Pumping Xenia, Starburst Polyps and Spaghetti Finger Leather Coral to name a few. Place these corals into the live rock as you did with the previous set of coral. Now you have succeeded in creating your reef aquarium. During the course of the 10 to 12 week mark, you may begin adding your fish to your underwater world. This will make it easier to keep clean, as Goldfish tend to be messy. Make sure that you rinse the gravel thoroughly before placing it in the bottom of the tank. If you have some decorations, you should add them now. Make sure that you rinse them well before putting them into the tank. Also be sure that the goldfish have plenty of room to swim, as they as active fish. As you can see these specifications are much more forgiving than those for certain tropical or marine fish. Guppies mature quickly and usually only grow to be about one and a half to two inches long. There small bodies and feathery fan like tails add a lot of interest to the tank. They are just fun to watch. Otherwise the lighting could range from day to day and algae will form. Try to position the saltwater aquarium away from direct sunlight as this will also add to the growth of algae. The key to maintaining a healthy saltwater aquarium is to keep it clean and algae free. By remembering the ways to avoid algae, you will be able to keep a healthy aquarium for years to come. Purchase an acrylic tank, because they are lighter in weight and easier to care for than glass aquariums. Also the visibility is better in an acrylic tank. If you don't already have a stand or a suitable replacement, keep in mind that you will need to purchase one. You will need a heater for temperature control, and a thermometer for checking the water temperature.