Let's drill down and see if I can figure out more. Sadly, most of these are not very scientifically done.
Things that I think had little to no effect:
2) Protein Skimmer: I have always run a protein skimmer and have never taken it offline. It is a Super Reef Octopus 250.
3) UV Sterilizer: I tried this for awhile. It didn't "solve" the problem, but mine was undersized anyway. Not a great experiment.
5) Macroalgae. I have this is in a well-lit sump. Caulerpa and cheato. Tried increasing the light cycle. This actually grew VERY LITTLE while dino was active. Once dino died out, it's growth exploded. My conclusion was that dino is more effective at getting nutrients from the water. Caulerpa noticebly outcompetes the cheato.
6) Lights out. Lights out visually works for quite awhile. The longer you do lights out, the longer it takes for the dino to reappear. In my most desperate phase I went for 14-15 days. Some coral died (surprisingly few however). The dino was out for a long awhile, but it came back. I think this just delays the process.
7) Hydrogen Peroxide. This did absolutely nothing for me. Nothing at all. Even with 3 times the suggested dose for several weeks. I am absolutely amazed that so many people reported this working. This didn't really do much to my coral either, except they were annoyed right after dosing. I would say the overall effect on the tank was zero.
8) pH. This was an early experiment. And man it sucked. I killed some pumps using kalk for this and maintaining a high pH for a long time. No effect.
Things that may have had some effect:
3) Nutrient increase. I think actually the nutrient increase is a RESULT of a the dinos disappearing and no the cause of it, but eventually there was a nutrient increase. However, when I deliberately had tried to increase them it did not seem to work in the past. Just food for thought. I think dinos would make an excellent filtration system for our tanks, if but only they could be isolated.
Squid, I think you made some good points of interest in this posting. I'd like to add some of my results using these methods to your points.
2) Skimmer: Always skimmed during my battle with ostreopsis. They didn't disappear until a couple months after taking my skimmer out.
3) UV: Tried it. Aqua UV 25w run with a Maxijet 900. It slowed them down but did not eliminate the problem. I don't think it's the answer because you are killing off the good with the bad. I even tried running it for a week at a time and then dosing various forms of bacteria.
5) Macro algae: Similar results. Algae stopped growing while the dinos were in bloom. I eventually had to remove the macro algae because they were just serving as another host for dinos to cover. I had both dragon's breath/flame algae and chaeto.
6) Lights out: good short term effect, but not a solution
7) Peroxide: no impact
8) pH: elevated with kalk and even dumped kalk slurries, no impact on the dinos and stressful on my coral
What finally worked??? Nutrient increase. No skimmer. Grew algae on a DIY turf scrubber and tried to get it established anywhere else I could. No water changes for about 2-3 months. Lots of mechanical filtration with a diatom filter. I tried to maintain nitrates and phosphate at low but measurable levels to benefit algae growth. I even, at times, dosed iron, nitrate, silicate, and potassium (all typical ingredients of fertilizer). I also added amino acids. Eventually, the dinos diminished and disappeared. I stopped dosing the extra nutrients and started water changes again. I've been dino free for about 3 months now and my sps have finally started to thrive. I have no doubt that there are still dinos there but some other life form is keeping them at bay.
