The lionfish hasn't stung me yet but bristle worms have pricked my figures a lot in the past. I've also been bitten by the clownfish a couple of times too so I find gloves to be necessary when putting my hand in the tank.
I've attempted elevating the Mg in my tank to 1500ppm and above in the past using a conventional 9:1 magnesium chloride and sulfate salt mix. Even after several weeks the bryopsis still persisted. Take a look on RC and you'll find many reports of people successfully getting rid of it with Kent Tech M. Here is one of them:
http://reefcentral.com/forums/showth...esium+bryopsis I tried to find a thread with one of Randy's posts in it but I'm running a little short on time. This product doesn't seem to work for everyone but for whatever reason it worked for me and Madreefer.
Edit: here is the original Tech M treatment for bryopsis thread from RC:
http://reefcentral.com/forums/showthread.php?t=1113109