How to Build an Aquaponics System

Aquaponics provides a living, breathing miniature ecosystem you can keep in your living room. At its most basic level, the system uses fish to supply nitrogen and other plant nutrients, while the plants help filter the water that the fish inhabit. You can use a small aquaponics system to grow indoor edibles or to feed an ornamental houseplant. Hardy low-maintenance fish, including guppies, goldfish and angelfish, work well for a first-time aquaponics project.

Growing tray

Drill

Aquarium gravel

10- to 30-gallon aquarium

Water pump

Tubing

Utility knife

Nail

Waterproof tape

Soilless potting medium

Air stone or pump

pH meter

pH adjuster

Turn the growing container upside down. Use a container 3 to 8 inches deep that is slightly wider and longer than the aquarium so it sits firmly on top. Drill 1/8-inch holes at 2-inch intervals, in rows set 2 inches apart. Drill a 1/2-inch hole in one corner for the pump tubing.

Rinse the aquarium gravel in hot water to remove any dust or dirt. Fill a 10- to 30-gallon aquarium with a 2- to 3-inch layer of the washed gravel.

Set the water pump inside the aquarium, resting it on the gravel. Use a pump specifically made for aquaponics or an aquarium pump with the capability to pump the water at least 3 feet into the air, such as one rated for 120 gallons per hour. Feed the pump tubing through the 1/2-inch hole in the bottom of the growing container. Loop the tube around the inside of the grow bed so it stretches the length of the bed, and then cut off the excess tubing with a utility knife. Mark the tubing where it enters into the grow bed.

Remove the tubing from the grow box and punch holes at 2-inch intervals along the length of the tube that fits inside the growing container, from the marked location to the end of the tubing, using a nail or other sharp object. Replace the tubing in the grow box. Fold over the open end of the tube and tape it closed with waterproof tape to seal it.

Fill the grow container to within 1/2 inch of the rim with a soilless growing medium, such as a combination of peat, perlite or vermiculite. These lightweight mixes are completely sterile and chemically inert, so they drain well without tainting the water in the fish tank.

Slide the grow container to the side and fill the aquarium with water. Turn on the pump to verify that all components are working properly. The pump pulls water from the tank and into the soil above, which then continuously trickles back into the tank through the drainage holes in the container. Adjust the flow rate on the pump until a continuous trickle is achieved.

Place an aquarium air stone or air pump in the bottom of the aquarium. Arrange the tube so it protrudes above the water. Plug in the air stone and verify that it is operating correctly and emitting small bubbles of air.

Insert a pH meter into the water and verify that the pH level is between 6.8 and 7.2. If the pH level is too high or low, add a pH adjuster formulated to raise or lower the level at the rate indicated on the package for the aquarium size and product brand. For example, add 1/4 teaspoon of the adjuster for every 10 gallons of water, wait 24 hours, and then test the pH level again before adding more adjuster as needed.

Place the fish in the aquarium 24 hours after achieving the recommended pH level, which also provides time for any chlorine in the water to evaporate. The number of fish will depend on the aquarium size and fish type. For example, 10 guppies can comfortably live in a 10-gallon tank. Leave the fish in their baggies and float them in the water for 10 minutes before opening. Add a small scoop of aquarium water to the bag and close it again. Allow the bagged fish to float an additional five to 10 minutes to allow them to acclimate before transferring them completely to the aquarium environment.

Adjust the grow box so it once again completely covers the top of the aquarium. Plant seeds or seedlings in the grow box, spacing them 2 to 6 inches apart, depending on the needs of the specific plants. Leafy annual vegetables and herbs, such as spinach (Spinacia oleracea) and basil (Ocimum basilicum) grow well in an aquaponics systems. Alternatively, use a perennial foliage houseplant, such as dumb cane (Dieffenbachia seguine), which when grown outdoors is hardy in U.S. Department of Agriculture plant hardiness zones 10 through 12.

Aquaponics systems require only basic daily feeding of the fish, generally with a single pinch of food formulated for the specific fish variety. You must also replenish the tank water every few days with chlorine-free water as the water level drops, and replace 10 percent of the water with fresh chlorine-free water once monthly.

Struggling fish, cloudy water or algae growth may indicate high levels of ammonia and nitrogen. Verify that the pumps are working correctly and that there are not too many fish for the space. Check the water pH and adjust it as necessary.