I am sure that you already know that a number of us here have dosed our reef tanks with 3% H2O2 for dinoflagellates. We used 1 ml per each 10 gallons of tank water daily for 5-7 days straight, as I recall. This worked for me, but I began dosing at the very first sign of dinos. I have also dipped coral frags in half H2O2, and tank water dips for a couple of minutes to remove nuisance algae from the plugs. Some corals did not like it, but most recovered in a couple of days. One can dip just the plug with as little of the coral going in the dip as possible to minimize coral exposure.