No need to go the expense of fluconazole... h2o2 works miracles with bryopsis.
If it's just the small tufts in the pic, then spot treat them. Cut the top off a soda bottle, cover the rock / bryopsis with it, use a syringe to inject the h2o2 into the top and then screw the lid on. Leave in place for 2 or 3 hours and then remove. Over the next few days the bryop will turn white and dissolve.
Get it now before it spreads!
If it's already spread, remove as much manually as you can, remove the rock and affected sand etc into a bucket filled with tank water and h2o2.
Try to get the 9% stuff, if not the 6%...