Raising the Mag will work, IF you use Kent TechM or Brightwell's Mg supplement, and it takes much longer than a week. It's not actually the magnesium that kill the Bryopsis. There some unknown impurity, in Kent TechM and Brightwell's Mg supplement, that's thought to kill the Bryopsis.
Most have had good results by raising their MG, to 1600, I went 1700. You'll need to keep it there for a fairly long period AND you'll need to do regular, large water changes, in order to be able to dose more Mg supplements. I've had good results, with the Mg overdose, though a few cautions, or at least words of warning.
Some corals will bleach. I noticed this with a lot of my Zoanthids, one Pocillopora, a Turbinaria Scroll coral and a couple of Acans. They didn't bleach, in the normal sense of the word. They actually turned a lighter, almost fluorescent color. It was pretty cool, actually...lol. All of the bleached corals will return to their original color, but it will take awhile.
Some have reported snails dying off. I didn't experience any die off, of anything, other than Bryopsis and a Turf Algae that I have. I have the Turf Algae in a few small areas in the tank. Only the Turf algae that receives direct light, died. It first bleached and then died.
Majano's bleached, but unfortunately, none died....lol.
I kept my levels elevated for about 3 months actually. I've read where people who've allowed their Mg levels to drop, at the 2 month point, have had the Bryopsis come back, quickly.
I raised my Mg, over a 4 day period. Some raise it all at once, thinking that the "Shock" is what does it. At day 6, my Bryopsis all bleached. The morning of day 7, I woke up to a tank without a trace of Bryopsis.
