The term hydroponics refers to any system that grows plants in nutrient-complete water without soil. There are many ways to accomplish this, and an expensive, commercially produced system is not necessary to successfully grow hydroponically. With a few buckets, glass or plastic jars, hoses and a means of pumping the water, backyard garden enthusiasts can make an inexpensive hydroponic system.
Cut the plastic bottle just above the point where the sides of the bottle start to curve in.
Paint the outside of the bottle using any ordinary house paint to block the light, leaving a vertical strip of about 3/4 inch bare so the fluid levels can be checked without taking the system apart.
Invert the top of the bottle that has been cut off and place it, upside down, on top of the cut bottle with the neck pointed downward inside the bottle. The top will be used like a cup to hold the perlite, peat moss or vermiculite and the plants.
Fold the 24 inch piece of cotton string in half and feed the fold down through the hole in the top cup, hanging the ends of the string over the edges of the cup on opposite sides. Cut the strings so that only 1 inch of string hangs over each side.
Fill the top cup two-thirds full with perlite, vermiculite or peat moss, looping and weaving the string through the growing medium and burying the ends.
Plant seeds or bare root plants into the growing medium, fill the bottom of the bottle with hydroponic fertilizer solution and place the planted cup on top of the bottle, making sure that the string hangs down into and reaches the bottom of the bottle. This string will absorb the solution and bring it up to the growing medium, which will in turn absorb the solution and deliver it to the plant.