1oz. per gallon is the proper amount for killing any constricting amount of algae, mostly the stuff that grows over and suffocates your roots due to light penetration. h2o2 only stays active for 15-20 minutes after its added to a reservoir anyways, so the levels slowly decrease.

All hydrogen peroxide is, is water with an extra oxygen molecule. Maybe when you plant drinks in the H202, its getting a little too much oxygen in its system, which somewhat simulates the effects of droubt.

Kinda like a human getting dehydrated from drinking beer.