Welcome to ATP, Crissy. I have never used peroxide to kill/control fungus gnats but I am sure there are those that can give you advice. I use yellow, sticky cards to keep my insects at bay. Here is one of those cards and it has been sitting next to my adeniums for not quite four weeks. It is easy to see the gnats, though more than one can count, but there are probably about 1/2 as many white flies stuck on the card as well. Both sides of the card is shown.
