i put hydrogen peroxide in my cloners regularly, and havent ever seen it inhibit root growth. in fact, ive noticed when used it actually PROMOTES root growth as it kills the bacteria that can attack your stems. ive got super skunk cuts i put in my cloner on the morning of the 18th i just checked and had to pot as they had 3" roots on them! in 3 days! do you know what hydrogen peroxide is? H2O2 basically breaks down into pure oxygen and pure water. wont hurt your clones a bit. you can even use it diluted if you have soil issues or rootbound plants 9diluted in water of course) to bring more oxygen to your plants roots.