I am making a rock wall for an aquarium and want to use waterfall foam to fix the rocks in place. I am using black lava rock so I want to use a brand that will keep the black color over time. I hear that many brands will turn a yellow or tan color over time and want to avoid this. I plan on pressing sand into the visible areas if that makes and difference.
Construction grade starts out pale yellow and turns brown-gold. (I just looked at mine, it has been in place for years, out of the sun). It is not UV stabilized, so should only be used where it will be out of the sun.
The black stuff sold for water falls ought to stay black.