Hydrogen Peroxide (H2O2) is a water molecule with an extra atom of Oxygen attached (2H2O + O2 = 2H2O2). This extra Oxygen atom is quite easily detached from the water molecule and eagerly combines with any suitable substance that has the room for it. For example it will attack organic blood cells.

Any chemists shop will sell you some concentrated 35% Hydrogen Peroxide, which may be diluted with water to give a 3% solution for human use. This diluted solution is good for treating minor cuts and scrapes etc. It is also used for softening ear wax. It works by oxidising the chemical parts that are presenting as having a free space for the Oxygen atom.

When H2O2 comes in contact with these impurities it will give a reaction which causes it to fizz. This fizzing is the Oxygen atoms coming out of their bond with the water molecules and bubbling out of the solution. As gardeners, we can use this eagerness to break its bond to help keep our plants free from everyday pests.

In the same way as old organic blood cells are attacked and consumed by the fizzing action of the peroxide, so will any bacteria and small insects be destroyed by a solution of up to 5% H2O2. At this strength it is safe for human skin but lethal to most bugs.

Mix up the following for a weekly preventative spray:
Add to 1Litre of Water:
30ml of 35% Hydrogen Peroxide
20 ml of Alcohol (Old style mouth wash works well)
2ml of wetting agent (Washing up liquid will do)
Use this mixture as a foliar spray to keep your plants healthy and free from bugs.

Another advantage of the Peroxide breaking down is that it releases free Oxygen into the area. So, if you were to add some to your nutrient tank, the dissolved Oxygen being released around the root system not only kills any bad root material and bacteria, but also oxygenates the roots with the excess Oxygen produced.

Plants can easily cope with a 5% H2O2 solution and because the mixture reduces to water in a short space of time, the dilutions are not that critical. For this reason, it also makes a great disinfectant for plant pots, greenhouses and grow-rooms.

It may be used at 10% for these jobs, but make sure to only use it if the area is plant free. A really great advantage is that you do not have to rinse it away after use because it will revert to water on its own.

Click the link to see how NASA is planning to use this sanitizing Hydrogen Peroxide system. http://www.primidi.com/2005/08/29.html