Turbos do seem to eat green hair, but if it gets too long, they may not go for it. The tooth-brush method should work.. but only if you can get the rock out of the tank. A safer way for the rock is to move it into a bucket of salt water and scrub it there. Then return it to the tank. While this will clean it off, it may not prevent it from returning. The key is figuring out the cause. High phosphates/nutrients in the system from somewhere.