How thick should my gravel in my freshwater aquarium?

BOWED I have a freshwater aquarium 80 gallons of measure 48 "long x 18" W x 22 "H

I like to use about 2 inches of gravel in all my systems (not including reef and OSD). To quickly estimate the amount freshwater gravel needed for an aquarium, aquarium simply multiple length (in inches) by width (in inches) and then divide by ten (the last hit digit is sufficient.) The resulting number is the number of kilos of gravel to cover the tank bottom to a depth of two inches. Thus, where appropriate, 48 X 18 = 864 … 864/10 = 86.4 pounds of gravel. I buy about 90 pounds for his bowfront and should give good coverage of gravel about 2 inches deep.

80 gallon reef tank aquarium