[tang daddy]

Its red bubble algae, you could try removing as much as you can with tweezers try to trim it to the root, then when the polyps are all closed up give it a dip in hydrogen peroxide mixed with salt water. I would do a 2/3 peroxide to saltwater ratio and leave in for 2-3 mins, the GSP is pretty tough and aslong as the polyps are all closed and not showing the skin of the GSP will be able to withstand the dip. After this you may want to use a tooth brush and some of that same water to scrub gently the infected area so as to make sure it hits the algae even more, good luck.

Alternatively you can use scissors and cut off the infected part, GSP will grow back no problem...