To make an outdoor hydroponics system, install bulkhead fittings in the bottom of the desired number of 5-gallon buckets, paint the buckets black to block out light, and cover the fitting with a filter. Connect black rubber tubing to each of the fittings, and connect the rubber tubing to a submersible pump. Place the pump in a reservoir that contains water and a nutrient solution, and place a layer of rocks in the bottom of each container before adding plants.
Cut furnace filter pieces, and place a piece of the filter over the bulkhead fitting on the inside of the container to ensure the growing medium doesn't enter the reservoir. Soak the rocks in a diluted chlorine bleach solution for one hour before adding the rocks to the container. Place the growing medium on top of the rocks.
Make a loop from flexible black pipe, and connect each bucket to the loop with additional pipe and a T fitting. Connect tubing to the T fitting so the tubing forms a loop around the top of the growing medium, and make small holes in the loop connected to the fitting to allow the nutrients to reach the plant.
To make a reservoir, paint an 18- to 30-gallon plastic storage tub black. Apply white paint over the black paint. When the paint is dry, connect the timer to the submersible fountain pump. Set the timer to the desired feeding schedule.