Just wanted to share a recent experience. I bought a frag from a local, dipped in Coral Rx before I added to my DT, and came home to a beginning dinoflagellate outbreak about 2 days later (yes, it was dinos...brown string with bubbles that you could almost watch grow when the lights were on). I panicked because I am OCD about my system and it was spotless...as in zero nuisance algae or other pests.
After a lot of reading and recommendations, I decided to do the 3% hydrogen peroxide dosing. I had been running lights for almost 12 hours so I drastically cut that to about 2 hours a day...basically, long enough for my tail spot goby to try to find enough to eat. After cutting the lights, I seriously didn't have enough diatoms to feed the fish so it started eating my pods, which is not what one wants when trying to battle a dino outbreak because pods eat the dinos. I ended up having to feed the tail spot. I also read the recommendation to not do water changes during an out break...after I did a water change and saw the dinos get worse the following day. I started feeding my LPS a little heavier (also read this should be done to combat a dino outbreak because it feeds the organisms that compete with the dinos).
Im going to estimate my system (IM 30L) to be about 26 actual gallons. For the first 2 days I dosed .1 mL per gallon (NOT 1 mL per gallon) which ended up being 2.6 mL total. It kept everything in check. I noticed when I would turn the lights on, there would be no dinos present but after the lights had been on a bit, I could start seeing them reappear and by the end of the abbreviated light period, they were growing in several places. Two other things I noticed was that my water looked SUPER clear and that my zoas and sympodium would instantly close up when I added it. I have several pieces of LPS (acans, chalices, and a duncan), two SPS pieces (birdsnest and lepto), zoas, mushrooms, pipe organ, and sympodium. The only things that seemed to be aware that I was adding it were the zoas.
On day 3 I upped the dose to 4 mL total and added this does twice that day (once in the morning and once in the evening). On days 4-7 I upped it again to adding this 4 mL dose 3-4 times a day. Again, nothing seemed to notice but the zoas and sympodium...possibly the pipe organ as well, but everything opened back up after about 30 min.
The dinos totally disappeared around day 4-5. For the past 2 days I have run a modified normal light cycle (I am keeping them on about 6-8 hours) and have seen zero trace of the dinos reappearing. My tank is SUPER clean and clear now, to the point where I am a little concerned that my snails and stomatellas are going to starve. To combat this, I may do a water change with some of my well water which I know is a bit high in phosphates, and hopefully that will start a dino bloom.
I will update this if anything changes, but I'm calling this a success story at this point. I will also be dipping future incoming frags in not only Coral Rx, but also a 50/50 mix of peroxide and tank water.