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. 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. 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. Since carbon dioxide is heavier than air it must be placed above the plants in order for it to drift down and surround the plants. Many growers use hydroponic techniques for food and ornamental plant production. Hydroponics doesn’t require a large water supply or fertile farmland for growing crops. You can grow vegetables and plants year round using hydroponic techniques. Hydroponic plants can be grown in basements, on an apartment balcony, or in almost any small space. Boric acid, manganese chloride, zinc sulfate, copper sulfate and iron sulfate can be used in minute amounts in the nutrient solution. Many people who grow their hydroponic plants in a greenhouse will also find that they need the correct amount of carbon dioxide in the air in order for their plants to flourish. Most newbie gardeners can either purchase an easy to install grow room or build a greenhouse outside of their home. Small grow rooms for the beginning hydroponic gardener are usually slightly larger than a closet and can be completely installed in under an hour. The cost ranges from several hundred dollars to over $500, depending on the add-ons that you think you will need.