I am losing most of my corals

[lost66]

I agree with @vetteguy53081 that it is cyano. I get it when I don't rise the frozen food before feeding it to the fish. Laziness sets in and I regret it when cyano pops up. I use chemiclean several times with no ill effects. I just follow the directions. My tank is a 210 gal mixed with SPS. Never had trouble with corals.

I dealt with cyano before using chemiclean multiple times. Always with a success. With current situation
that brown patch doesn't go away completely. I even used it twice to see maybe it was too thick but no, it is not cyano, something else is going on - dino. Microscope confirmed dino.

Embarrassing to say, but other than my Hammer corals, I don't know what any of my corals are. The frag looks nice, I buy them and see what they turn in to.

You are brave I wouldn't do that with my tank, I need to know what I am putting there.