I used a mix of arginite and quickrete play sand.
the play sand it a brownish color but smaller than the arginite so it moves to the bottom of the tank.
SD is hard to find in locations but I have heard that you can order it but have to buy it by the pallet or something like that.
Mike
ey..i just bought some playsand at HOME DEPOT....it comes from the beach in Monterey, CA and processed there ...kiln dried and very fine....mesh30 is whats on the bag.....for 50lbs it cost 3 bucks.