I avoid using the common 3% hydrogen peroxide you normally find at drug stores. This is because such low percentage 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 make up my mind to use 35% hydrogen peroxide instead.
The above 2 paragraphs where taken from the url below.
Using Hydrogen Peroxide in Your Hydroponics Gardening System