It can be used outdoors in a greenhouse but the bug problem and their potential diseases need to be addressed in order to save your plants from their adverse effects. The most popular method of generating carbon dioxide for your hydroponic plants is the use of a pressurized carbon dioxide system. The equipment is relatively inexpensive (under $500) and the operating expense is low. There’s no need to worry with predator insects, because most will not harm your crops. Your garden should also be able to support the predator insects. Many biological insects will not survive if the temperature is too hot, or if there isn’t a good source of water. Other ways to protect your hydroponic produce against spider mites include using non-toxic yellow sticky cards. By the 1970’s, scientists and analysts wee not the only people interest in hydroponics. Traditional farmers and eager hobbyists began to be attracted to the virtues of hydroponic growing. Some of the positive aspects of hydroponics include the ability to produce higher yields than soil-based agriculture and they allow food to be grown and consumed in areas of the world that cannot support crops in the soil. It uses much less water than conventional gardening and does not erode the soil or add toxins to the environment. Soluble nutrient formulas are re-circulated and used by the plants’ roots, which helps eliminate environmental waste. As many gardeners today are choosing to grow organically, organic crop cultivation in hydroponics has become very popular. The plant roots are suspended within the water by various designs and the crop obtains the food nutrients directly from the water, or from an air mist sprayed directly unto the plant roots. Hydroponics also requires the use growing media. Hydroponic systems use various mediums that are composed from relatively inert materials that have the ability to retain the food rich moisture and have the ability to physically support the plant roots. PH is a measure of how acidic or alkaline the nutrient solution or water is. The pH scale ranges from 0 to 14, 7.0 neutral, and 7 to 14 alkaline. General plants prefer the pH to stay in the 5.5 to 7.5 ranges as going beyond this range inhibits certain nutrients to become less available for the plant to absorb.