Dinoflagellates are a real pain. I have been trying to keep mine under control with some success (I have tried Dino X, Hydrogen Peroxide, lights out but my SPS always suffer with that).
At the end of the photo period I cover all the sides of my 150gl tank, I will not allow any light from TVs lamps, etc enter the tank.
I only dose organics and trace elements (also do water changes) after lights out as they seem to fuel the growth of dinoflagellates. (I used to do the same with carbon dosing but PH would drop further during night and my PH is already on the low side at night.
Once a week I stop all the pumps and flow in the display tank, few minutes later the dinos start floating, coming out of pumps/rocks, etc. That´s when I dose a flocculant, turn all the pumps and let the skimmer get rid of some.
A month later and I only have some that love to settle on my two gyre pumps. I don't understand why but my gyre pumps are like magnets attracting the dinoflagellates.