When I had a bryopsis outbreak a couple years ago, I used Seachem's Reef Advantage Magnesium because I already had it on the shelf, and I did not trust the impurity level of over-the-counter epsom salts. At that time this treatment possibility was just beginning to be discussed, and I'm almost certain that there was not yet any recommendation of using Tech M. I used every grain of the R.A. magnesium I had (+/- 300 gm) to raise the system's 85 gallons of water to a mg level of 1800 and hold it there for just short of two weeks, but I now have no bryopsis in that tank. At the time, I saw very little evidence of the mg working. I can't say for certain that it was the magnesium that killed off the weed, but something did. Maybe the derbesia just just starved it out...
