If you are a beginning hydroponic gardener you may want to use the pre-mixed nutrient solutions and observe their effects before you begin to make your own solutions. The basic nutrients needed in any hydroponic solution are potassium phosphate, potassium nitrate, calcium nitrate and magnesium sulfate. Hydroponic gardening requires an energy source in order to grow. Usually, natural sunlight is used, but during the shorter and darker days of winter, many hydroponic gardeners use artificial lights to increase the intensity of light or to expand the daylight length. Different types of artificial lighting are selected for specific plant varieties and optimum plant growth characteristics. Growing media for hydroponics includes, expanded clay, rockwool, perlite, vermiculite, Styrofoam, sand, pea gravel, and other mediums. There are many types plants that can be grown in a hydroponics system. Some plants will grow better in hydroponics system than others. Many growers use hydroponics systems to grow tomatoes, lettuce, watercress, cucumbers, herbs, and various other edible plants. Hydroponics is always a soil less culture, but not all soil less cultures are considered to be hydroponics. Many of these cultures do not use the nutrient solutions, which are required for hydroponics. There are two main types of hydroponics, which are solution culture and medium culture. Solution culture uses a nutrient solution but does not use a solid growing medium for the roots. Many different civilizations have utilized hydroponic growing techniques throughout history so they are not a new method of growing plants. Giant strides have been made over the years in this innovative area of agriculture. Throughout the last century, scientists and horticulturists have experimented with different methods of hydroponics. Maintaining the proper pH level in the nutrient reservoir is most likely the single most critical factor to successful hydroponic gardening. If the pH factor goes too high or too low, the plants will not do well and will show confusing signs or nutrient deficiencies. Nutrients are a key factor in a successful hydroponic garden.