Dry ice, which is solid carbon dioxide, is effective when used in a well-sealed area. The ice can either be used in block form or broken down into small pieces and used a little at a time. Another method is to put the dry ice into a Styrofoam container with holes in it to slow down the rate of evaporation. 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. 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. The key is to monitor the nutrient solutions on a regular basis to make sure the pH is at the right level. Hydroponics is the practice of growing plants without soil as hydroponics cultivates plants in nutrient-rich water. For optimal growth, the amount of light your plants receive can be the difference between life and death. Too many lights can dry out your plants while too few can have your plants stretching desperately towards the lights. All plants respond differently to light depending on the intensity, wavelength and duration it receives. The electricity consumption is environmentally damaging and expensive, and expense is another area where hydroponics comes under the gun. The nutrient mixtures and growing mediums used can be very expensive. While research is happening to try and bring the costs down, and there are some promising leads, like the field of aquaponics, hydroponics is currently financially prohibitive for some. When growing hydroponically, the gardener will need to add all of the nutrients the plant needs to the water. Distilled water will work best for making the nutrients. Hydroponic supply stores sell a variety of nutrient mixes for specific crops and growth cycles. Plants can be propagated by a number of methods.