its important we wouldn't try and cure it In one pass we would model the expected kill and sustain on a side of the rock and set back, comparing to unworked areas.
many real reefs in fine shape look like that, its quite nice actually. our eyes for marine tank keeping are trained to want it another way, but its very natural looking and you have 1.6 million pods in that.
your sandbed status directly means you should not use animals to fix this. they relocate plant mass as waste pellets to be sinked further.
it should be modeled kill, proven, then whole tank rip cleaned bottom up per our 40 page rip clean skip cycle thread, the rock detailed, set back this time knowing how its going to work on top of clean sand, with no mass to rot inside the tank.
fluconazole is likely to kill it, however your waste compounding will be stratospheric and literally nothing can work better than the rip clean above. you can get bandaids that turn into a year long cyano battle, but you can't beat a rip clean for the specifics shown above.
if you choose test rock let me know and we'll work the area in a unique way.
its not about adding peroxide on top of the plant or adding it to the water. there is a surgical way that is likely to really help, in the test spot.
notice how all other methods subject your whole tank to a maybe...or they compound waste never mentioning the root of the issue along with unlucky hitchhiking
