if you can remove them, i.e. not glued, I would take a tooth brush and try to scrub off as much algae as you can. You could also try dipping the brush in hydrogen peroxide prior to scrubbing. I've had some good success with that.
if you can remove them, i.e. not glued, I would take a tooth brush and try to scrub off as much algae as you can. You could also try dipping the brush in hydrogen peroxide prior to scrubbing. I've had some good success with that.