This is my first 5 gallon bubbler bucket set-up and I'm concerned about light getting through the floral foam and then to the roots, ....at any stage of the growing cycle. I read an article on line where some guy put dark sand on top of the growing medium. He wasn't using floral foam I think it was lava rocks or perlite. I think the idea is good, but not dark sand-on floral foam. What else could be used, and not make a mess during leaching/wash down and block light out ?......

White plastic.

i bought an igloo ice chest and cut two holes inthe top.
cheap like 20 bucks and has drain plug and keeps everything dark.
plants grow great

I put a layer of foil over the rocks/rockwool...no algae, no nats and the foil is a good light reflector from the bottom...any opaque and waterproof material would be fine...I've seen plastic squares white on one side and black on other cut to size of rockwool cubes for the same thing...I like the foil, it works fine...