These worms are easily spotted and usually appear as circular spots on the coral's vesicles. They are not a cause for alarm and usually do little damage if any. However, if you notice a significant amount or a large population of these worms, you will have to take action as they could cause death. Coral is a wonderful addition to any aquarium. This should help to reduce the amount of stress caused to the fish. Change about a third of the water in the aquarium at a time, because this type of change will cause the least amount of disturbance to the fish and other inhabitants. This will need to be done every two to three weeks. Use either a bucket or a siphon to remove the water from the tank. Use plastic or rubber scrubbers, rather than metal to clean the sides of an acrylic tank. Be careful not to accidentally pick up a piece of substrate or gravel while cleaning the inside of the tank. However, if you do happen to scratch an acrylic aquarium, all is not lost. The tank can be repaired, unlike glass. As the water in your Goldfish tank ages, it builds up beneficial bacteria that turn harmful chemicals excreted by the fish into harmless ones. However, this will take some time. Start out with only one fish. The nitrogen cycle will not begin until you add the fish, so running an empty tank for several days will not help. 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. This is especially important in new aquariums that lack nitrifying bacteria. Test the water P.H. every day within the first month. Watch the tank for cloudiness; if the aquarium becomes cloudy, it may be necessary to add a clarifier. If water is removed during this process, be sure to replace it and keep the water in the tank at the same level. Add chemicals and chlorine weekly so the balance within the tank remains the same. At this time, it is best to test the water for the ammonia and nitrate levels. Don't overlook testing the pH of the water as well.