In the northern hemisphere, most south facing windows should provide adequate light during the summer. During the winter the light levels may fall low enough so that plants no longer grow. This can be remedied by adding artificial light to increase the day length. Most plants need 12 hours of light a day to thrive. Water - Your supply of fresh water may be unsuitable to plants.
Most city waters have chlorine or chlorine byproducts that can cause problems with young plants.
It is best to do beginning experiments with distilled or purified water. Temperature - The plant has two basic temperatures, the media temperature and the air temperature. For most food plants the temperature should be from 60 to 80 degrees F. Lower temperatures reduce growth considerably. Nutrient - Bradley Hydroponic Nutrients have been designed to be fault tolerant. That is, a buffer has been added to the nutrient to maintain pH at a 6.5 to 7.0 level.