Your decision will impact the type of gravel or sand you will use as well as the pH of the water within the tank. Armored catfish prefer soft bottom material because they forage for food within the substrate. Catfish feel more secure when they are hidden from the light, so be sure to have caves and hiding places for this type of fish. Also be sure that the goldfish have plenty of room to swim, as they as active fish. Give them a place or two to hide, and that should do nicely. Now that you have everything in place, you can add in the water. You will need to use a dechlorinator, as the chlorine in tap water is poisonous to fish. Once the fish tank is filled up, you can turn on the filter. 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. Monitor the fish for signs of stress or illness. A healthy fish will be swimming regularly. There is not much wiggle room when it comes to these specific staring points. In order to avoid a costly mistake it is important to be patient, watch the tank closely, and make sure that you don't introduce any marine life until the tank is absolutely ready. Once the aquarium is ready, start with anemones and clown fish. Allow about thirty days for these fish to become acclimated to the tank, before adding any new fish. It usually takes about thirty days for the symptoms of ich or other fish illnesses to show up. It is important to make sure that all existing fish are healthy before adding any new species. The transportation of new fish itself is stressful enough, without having to add disease to the situation. The ammonia levels should return to zero. This also takes about a month. There are a few basic tips that will keep fish healthy. Don't over feed the fish. Any excess food will become debris in the tank, and then turns into ammonia, which is toxic to fish. Change the water in the aquarium regularly. Replace approximately one third of the water in the tank every two to three weeks.