That's somewhat of a late response, but I'd be guessing about 80-100 pounds would be in the right ball park. Frontosa look great over black substrate, but have you looked into SpectraQuartz? Google the term for more info. It is basically the same as 3M ColorQuartz (now discontinued) which a lot of people have used in their tanks. It's available in black, and a great deal cheaper than Tahitian moon sand. I've had it in my 240G Front tank for about 5 years now, and couldn't be happier. The Fronts love it too :thumb: