magnesium is what i just used. And it is all gone. Assuming what i had was bryopsis. You dose it slowly to raise your magnesium up to around 1650 and then maintain that for a week or two to make sure it is working. I started noticing die off around 1400ppm. My magnesium was kind of low to begin with. But it did the trick. I no longer dose it and i have no more hair algae nor bryopsis.