How to Set Up a 20-Gallon Aquarium

1). Rinse out the tank, using water only, because soap can leave a toxic residue.
2). Pick a spot away from vents or windows to set up your aquarium. It should be near an outlet so you can easily plug in the aquarium equipment. You'll need a sturdy stand for the aquarium, wherever you put it. For a 20-gallon aquarium, choose a stand -- or even a small table, that can support about 200 pounds.
3). Rinse the aquarium gravel. For a 20-gallon aquarium, you'll need 20 to 30 pounds of gravel. Spread the gravel evenly in the bottom of the tank.
4). Rinse any plants or decorations you plan to use, and arrange them in the aquarium. The decorations and plants will provide decor only. However, if you have plan to have fish that require many hiding places, add extra decorations and plants.
5). Fill the aquarium with room-temperature water until it's almost full. To keep the gravel level as you add water, place a small dish in the bottom of the aquarium, and pour the water onto the dish. Remove the dish before you've completely filled the aquarium.
6). Install a small heater. Choose one that is specifically designed for a 20-gallon aquarium -- immersion heaters usually work well. You may also want to install a thermometer to monitor the aquarium temperature.
7). Install the aquarium filter. Again, select a filter that is designed for a 20-gallon aquarium. External power filters, which hang on the back of the aquarium, work well in 20-gallon aquariums. Most filters have a built-in air pump, which aerates the water. If your filter doesn't have this feature, install an air pump, which connects to an air stone.
8). Add an aquarium hood with a tank light in it. Many aquariums come with these hoods, and you will only have to buy the light bulb, which can be purchased at a pet store.
9). Fill the aquarium all the way to the lip of the aquarium hood if you have not already done so.
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Plug in the heater, filter and tank light.
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Wait several days before adding any fish, allowing time for the tank's life-sustaining nitrogen cycle to develop.