Thats a GREAT observation... on fish behavior...
I had not thought about that before now..... makes total since .....
I personally have never seen the gray sand.. if someone here
has this style..
I would really like to see it in a tank.. ( I am Curious )
I failed to tell anyone.. about this cichlid tank..
in order to Buffer the PH at a steady 8.0
I have included a total layer of Crushed Coral under the sand....
I made the sand very deep so that the Crushed Coral will stay
at the bottom.
I have had some great luck with Crushed Coral keeping the
PH at 8.0