Bryopsis grows like a fern plant and the best way to remove it other than to manually remove ALL of it INCLUDING the root system is through the use of hydrogen peroxide. This procedure can only be accomplished however, by removing the rock, equipment from the water. Apply the hydrogen peroxide to the root system and let sit for 3-4 minutes, then you can put it back in your tank. The Bryopsis should be gone in about 72 hours. Once killed it will not grow back again UNLESS it is reintroduced into your tank via live rock, coral or frag plug typically.