You can kill anything with PP !
If you are doing this outside a tank with no fish then yea just OD the gravel and be prepared to rinse..
I OD tanks when I switch fish around if I am worried.
I make the tank so purple it looks black for a couple days..
Then I change water and hit tank with H202..
Like most meds or oxidizers the more you use the larger the form of life it will kill.