Darn, thought I had it.....
If you have an air compressor or can borrow one, maybe you can get the tip of the line down there (of course disconnect air compressor from electricity as you never know) and blow air and this may stir things up. The tip is small (maybe 1/4 "). I use compressed air to move things around in a car, around the garage, etc. The best is my Red Maxx blower to dry a car (which will not work in this case). It appears you have algae inside the light and the trick is to get in there to break everything up so the bleach can do the trick. Keep us posted!