Picture in post #16 is better and I would say, partly because it's the most common flatworm, is that you have rust brown flatworms. I'd suggest getting rid of them with either a fish that eats them....wrasse.....or chemically with something like Flatworm Exit. They multiple quickly and can produce a toxin.
I am also reading these aren’t so bad too.
So much conflicting information when I ran a search for them.
If I were to nuke the tank with salifert, could I remove as many corals as possible, dip (regular coral dips) them in another container and keep them there while I hit the tank with exit?
Top is secure and I also have the little magnet plug for the feed hole.
Which fish would attack these more aggressively, and I understand that is subjective, but wondering if the coris or six would be more effective at eradicating these flatworms?