Algae ID & Help

[Amateur Reefer]

I have been battling this algae (brown cyno?) since treating my tank with Fenbendazole to kill off Xenia. Tank also sometimes gives off a musty smell, making think it *could* be some sort of cyno. My zoas and pallys have seem to have died since treatment and this outbreak as well. Any help IDing what exactly it is (diatoms, dino, cyno, something else) and possible treatments?

 

[Alex Cataldo]

Looks kinda like cyano and I solved that by cleaning the sand. Usually there’s a lot of bound up nutrients just rotting and making a habitat for the stuff on the sand

 

[Amateur Reefer]

I'm on my third dose of @Fauna Marin Dino X, and there is no dent. I've also tried dosing some H202 the past couple days. Still no improvement.

GFO is off per Dino X instructions and Phosphate is now .29 (Hanna) and Nitrate is 40 (API).

Is the next step complete black out, if so, how long and will it just come back afterwards?