There are two main reasons for using Hydrogen Peroxide in your hydroponic system. The first is to add extra Oxygen to your nutrient reservoir. Nutrient absorption only occurs in the presence of Oxygen, which is the whole idea behind aeroponics...the increased Oxygen levels (and absence of grow media to struggle against) lead to increased growth rates. In a deep water culture system, Hydrogen Peroxide can be used with some success to add extra Oxygen to your system.
In a deep water culture system, you do not want the nutrient solution to go above 72 degrees. Warm water holds less dissolved Oxygen, and therefore encourages the growth of more viruses, fungi, and anaerobic bacteria. Using Hydrogen Peroxide adds Oxygen to your water and cleans the water of pathogens. Benefits include healthier root systems, increased nutrient uptake, thicker stems, and bigger leaves.
One expert claims it should be used on all soil gardens as well as in hydroponic systems. Knowing as much as I do about beneficial fungus and micro-organisms and the benefits they provide to living plants, I am shy in taking this advice. However, when this first line of defense fails and plants become sick I often resort to using Hydrogen Peroxide treatments on my soil grown plants.
The chemical formula for Hydrogen Peroxide is H2O2. You may notice it is simply water with an extra Oxygen atom. In fact, as Hydrogen Peroxide breaks down in a solution the result is Oxygen (O2) and water (H2O). Its application helps deliver Oxygen to over-watered plant roots and helps to sterilize the growing media by killing harmful anaerobic (not Oxygen compatible) bacteria and pathogens that cause disease. This includes bacterial wilt, Pythium fungi, Fusarium fungi, and others.
I avoid using the Hydrogen Peroxide you commonly find at the local drug store. This is because such low percentage (3%) solutions are unstable, and chemicals are added to the Peroxide to keep it from breaking down before it can be used. I did a little research because I did not know what chemicals were used for this, or if the plants uptake these chemicals, or if there was a health risk associated with any of these stabilizing chemicals.
Hydrogen Peroxide is usually stabilized with Acetanilide. Acetanilide is a synthetic compound that was first used for its fever reduction and pain killing properties in the late Nineteenth Century. For many years it was utilized as an alternative to Aspirin to treat various ailments, but large scale medical use stopped when the toxic side effects of consuming Acetanilide became apparent. This was enough to convince me to use 35% Hydrogen Peroxide instead.
Firstly, 35% Peroxide is caustic and should be treated with the same caution as a strong acid. 35% strength Hydrogen Peroxide should be readily available at any quality hydroponic supply shop. The stronger concentrations do not use the added stabilizers.
The recommended dosage is to add 2-3 ml to each gallon of water, however, I use 5 ml per gallon and have never had any problems. At every nutrient change treat your fresh water using Hydrogen Peroxide. The general idea is to let the hydroponic system circulate the Hydrogen Peroxide solution for about a half hour to let the Peroxide work against pathogens and to let the solution stabilize before adding your nutrients.
The beneficial effects of using Hydrogen Peroxide last about 4 days. There are some gardeners who add a little Peroxide to their nutrient reservoirs every 5 days in between nutrient changes. If you decide to do this, stick to the guidelines and always make sure your solution is thoroughly mixed before exposing your plants roots to it. Another option is to top off your nutrient reservoir with peroxide treated water whenever it is low.