Examples of hydrocarbon fuels are propane, butane, natural gas and alcohol. Fuels that contain sulfur or sulfur compounds cannot be used because they produce harmful by products when they burn. Dry ice can be used in small greenhouses, especially if a cooling effect is also desired. Dry ice, which is solid carbon dioxide, is effective when used in a well-sealed area. Hydroponically grown plants are not immune to spider mites, but they are more pest resistant than plant grown in soil. Plants grown in hydroponics are usually healthier than soil grown plant, because hydroponic plants are fed their exact nutritional requirements. The natural preventive measures against spider mites are used in most hydroponics systems. As you progress in your hydroponic garden hobby you may also want to switch from an aquarium pump or bubbler system to a more advanced irrigation and drainage system for your garden. Once again, the more plants you have the more advanced equipment you will need. If you are still unsure about starting a hydroponic garden, you can get everything you need in a little kit called a plug-and-go hydroponic gardening kit. Hydroponics is proven to have several advantages over regular soil gardening. The growth rate on a hydroponic plant is 30 to 50% faster than a soil plant that was grown under the same conditions. The yield of the plant is also greater. There are many reasons for the drastic differences between hydroponic and soil plants. The energy saving poly greenhouse covers, the PVC pipe used in the feed systems, and the nutrient injector pumps & reservoir tanks were all made of types of plastic not available prior to the 1970s. As both small and large hydroponic farms were established in the late 1970s, it was proven that hydroponic culture could produce premium produce and be a profitable venture. The water consumption in hydroponic growing is significantly less than traditional growth methods; in many cases, hydroponic crops use a tenth of the water of equivalent traditional crops. Also, the water that is used is used more effectively; in hydroponics, weeds do not steal part of the crop’s water supply.