I added 6 inches of cheap fine play sand to one of the ends of the tank for my melanurus wrasse to play in, and to add a bit of biofilter. The sand looked brown under sun light but is a pleasant lunar-surface grey under the reef lights. I didn't do 6 inches over the entire tank because I wanted to preserve the visual impact of the tall rock work, and I like the look of the sand slope on the one side.
SUNLIGHT
REEF LIGHT
