To set up an aquarium, choose a spot that doesn't receive direct sunlight, and place the tank about 5 inches from the wall to leave room for the filter. Next, clean the tank with fresh water, and rinse the gravel with water until the water runs clear. Do not use soap or detergents, which are highly toxic to fish.
Add the gravel to the tank so that it slopes gently towards the front of the tank. Add room-temperature tap water until the tank is about a third full, pouring it slowly over a plate to avoid disturbing the gravel. Add a dechlorinating agent, such as Tetra AquaSafe.
Install the air pump and air lines next. Use a check valve on the tubing to prevent water from backing up into the pump if the power is turned off. If a check valve isn't available, place the pump above the tank. Set up the heater, but don't turn it on yet. Add rocks, decorations and any live plants, leaving plenty of room for the fish to swim around and several places for them to hide. Place the roots of the plants under the gravel, leaving the top of the plant exposed. Add an aquatic-plant fertilizer, such as Tetra FloraPride, to promote plant growth.
Set up the filter, making sure to prime it with water from the tank. Add water to fill the tank, and turn the equipment on. Wait 24 hours for the water temperature to stabilize, then add some fish. Start slowly, adding about 1 inch of fish per 5 gallons of water. After about four weeks, test the water. If the ammonia and nitrite levels are zero, gradually add up to one 1 inch of fish per gallon of water over the next few weeks.