How to Keep Freshwater Tropical Fish

Decide on the types of tropical fish you want. For beginning aquarists, among the best choices are gold and cherry barbs, bloodfin tetras, zebra danios, members of the killifish family--which include platies and guppies--and labyrinth fish, such as dwarf gouramis. These are all colorful, hardy, active little fish which get along well in a community, are fairly easy to feed and thrive in temperatures from 74 to 79 degrees Fahrenheit. Keep these fish in groups of four or five members, not only to promote a feeling of security for the fish, but for the visual effect of a school of similar fish moving in concert. Allowing two gallons of water for each inch of fish is a good rule of thumb; depending on the adult size of your fish, you can have two small schools in your 20-gallon tank.

Select a location for your aquarium and stand in a place unaffected by vents, heaters or sun. Make sure the stand is sturdy; with water weighing 10 pounds a gallon, the stand will be supporting over 200 pounds.

Rinse the new aquarium, and everything that will go in it, with tap water. Do not use soap of any kind. Aquarium gravel can be rinsed in a pasta colander. You will need about a pound and a half of gravel for every gallon of water. Place the gravel in the bottom of the aquarium.

Use live aquatic plants to landscape your aquarium, affixing their roots into the gravel before you add water. Live plants not only create a more beautiful, natural environment, but help maintain water quality by removing ammonia and nitrates. Good choices are hygrophilia, which has graceful, elliptical leaves; vallisnera, with long, narrow leaves that make it a natural for placement as a backdrop; and Java fern, which features lush, wavy leaves. Because Java ferns tend to float, you may need to anchor their roots under a decorative rock.

Install the filter and heater, but don't plug them in yet. Put a saucer in the middle of the tank, and pour water that you have treated with a dechlorinator over the saucer in order to prevent displacement of gravel. Fill the tank partway, rearrange any plants or decorations that have been disturbed, add the rest of the water, and remove the saucer.

Plug in the heater and thermostat after giving the thermostat 15 minutes to adjust to the water temperature. Plug in the filter. Add the reflector hood and light, and plug that in too.

Let the water cycle for a few days before adding fish, checking thermostat and thermometer to make sure the heater is keeping the water at about 74 to 79 degrees Fahrenheit. Use a water-testing kit to monitor the levels of nitrates, chlorine, ammonia and other chemicals. This will tell you if it is safe to add fish to your new aquarium.

Introduce your new fish to the aquarium--a few at a time over the next few weeks--by floating the plastic bag they were sold in in the water for at least an hour in order to equalize water temperatures. Open the bag several times to let aquarium water in, so the fish can gradually acclimate to it.

Add a scavenger fish to provide interest and motion at the bottom of the tank and to help to keep the tank clean. Chinese algae eaters, Plecostomus catfish, and coolie loaches--particularly appealing with their colorful stripes--are all good choices.

Feed your tropical fish a good-quality commercial flake food, supplemented with brine shrimp and bloodworms to promote good heath and bright colors.

Keep algae from the sides of the aquarium by using a commercial algae remover and occasionally scraping the sides of the tank with a razor blade. Every few weeks, use an aquarium vacuum to clean the gravel. Periodically, 20 percent of the water should be siphoned out and replaced with fresh dechlorinated water; use your water-tester kit to tell you when this needs to be done.