You might want to let the filter run in the new goldfish tank for a day or so to filter out any chemicals or dyes that might have been left on the gravel and decorations that you just added. Waiting to buy new fish can be one of the hardest things about fish keeping! You need to add fish gradually. Fish excrete ammonia. These types of aquariums usually consist of shrimp, prawn, hermit crabs and perhaps even starfish or sea cucumbers. The third type is the fish and invertebrate saltwater aquarium. These are more difficult to maintain than either of the two categories separately. Certain invertebrates feed on certain fish, and the reverse is also true. The decision to use live plants should be a primary one and steps need to be taken to prepare the tank for later use. It is suggested to add all your plants in the beginning and let them become established. By doing this, you will eliminate the chances algae utilizing the nutrients added and the extra lighting. It is a good idea to test the ammonia and nitrite levels before adding fish to the aquarium. Begin by adding only three to four small fish. A general rule is to wait another thirty days before adding additional fish, because that is the incubation period for most fish illnesses. In addition, test the nitrite and ammonia levels before adding these additional fish. Most plants will not survive if there is too much debris or waste in the water, so keeping up with cleaning is essential. Once your plants are established in a clean, well lighted tank, you must care for them by making sure they receive the nutrients required for healthy growth. Plants need both macro- and micro nutrients. Invertebrates should be fed more frequently in smaller amounts than fish. Try to feed only an amount that can be consumed in the first thirty to sixty seconds. When setting up an invertebrate tank remember to include live rock, because some invertebrates feed on the parasites that grow on the live rock.