There are two basic divisions between systems: water culture and media based. Systems may also be active or passive. Active systems use pumps and usually timers and other electronic gadgets to monitor the operation. Passive systems may also incorporate any number of gadgets. These systems try not to use pumps and may rely on the use of a wicking agent to draw nutrients to the roots. Air pollution can affect the growth of your greenhouse plants and must be monitored if you live in a large city. Signs of air pollution include spotting or twisting of the plant’s leaves, flower and bud fall off, and unusual discolorations as well as poor growth can signal a problem. Remember, plants are affected by the following elements: air, temperature, light, water and pollution. The basic items you need after you decide on either a grow room or greenhouse include a temperature control unit, exhaust fan, heating mats, light fixtures for your blue and red spectrum lights, an aeration system (an aquarium system works well for small gardens), pearlite, marble and Styrofoam work well as a beginning medium and rockwool, oasis or Rapid Rooters. Hydroponic gardening helps to eliminate the need for weeding and helps to cut down on diseases and pests. This form of gardening is also easily adapted to indoor environments, which means it can be used throughout the year to grow a gardener’s favorite plants. The greatest advantage to hydroponics is the overall outcome of the plants, which will be of better quality and are much healthier. The History and Growth of Hydroponics Hydroponics means working water and comes from the Greek words “hydro” and “ponos,” meaning water and labor. Many different civilizations have utilized hydroponic growing techniques throughout history so they are not a new method of growing plants. Plants are able to change their own cellular pH level to stop or help speed up a certain enzyme reaction. The electrical charges in soil particles are different from those in mixtures with no soil. Because of this reason, different pH levels for nutrient uptake are needed for each type of growing medium.