You really need to be careful to know the concentrations that you're dealing with whenever handling any sort of chemical like peroxide. For example, 1.5% peroxide is 1500 mg/L, and that's MUCH higher than any plant would be able to handle. If I recall correctly, when getting rid of algae people use something like 75 mg/L H2O2. Try not to do anything like this again without researching the chemical and its proper usage.
It's not bomb grade plutonium. No need to scold me.