Videos
Motion is one of the best clues for identifying a dinoflagellate. These are my microscope videos.
They are all on my YouTube channel (YorickSanchez). The magnification is the objective times the 10X eyepiece, plus any camera zoom.
Ostreopsis
Look for the cells spinning around a fixed point like a tetherball. See the Ostreopsis page.
Amphidinium
Look for the cells gliding smoothly along the surface, and for the grooves at the top of the cell. See the Amphidinium page.
Predation
A practical walkthrough
My videos are mostly raw microscope footage. If you want a polished, step-by-step video about finding and dealing with dinos in a reef tank, this one from Reef Rookies is worth your time. It is another aquarist's guide, not mine, so you may notice differences from my notes on the treatment page.
From other aquarists
Aquarists who sent me their microscope videos have given permission to share some of them. You will find them on the Amphidinium, Prorocentrum, and other dinoflagellates pages.
More
A video of Symbiodinium is on the other dinoflagellates page.