O.k., here I go with the Tech M Bryopsis solution. Here are my parameters now:
Calcium 450
Alk 5.8
Magnesium 1300
I'm going to do a water change first (trying to get the alk up to at least 7) and then begin dosing 160 ml per day of the Tech M while monitoring all three buffering parameters. This should bring my Mag up 18.3 ppm per day. I'm going to bring it up to at least 1600 and am going to keep a good eye on my sps and other inhabitants.
I'm also on the Brightwell Bacter7/Vodka program. I'm very happy with those results. Here's hoping this shortcut to killing Bryopsis isn't a bad idea.
I didn't take pics because I just did a harvesting and there's not much left except strands.
I'll keep you posted.