Aquatics Unlimited: Articles: How Much Gravel?
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How Much Gravel?

for the week of 7/30/98

To quickly estimate the amount of freshwater gravel required for an aquarium, simply multiple the aquarium's length (in inches) by it's width (in inches), then divide by ten (whacking off the last digit will suffice). The resulting number is the number of pounds of gravel that will cover the aquarium bottom to an average depth of two inches.

For example, a standard ten gallon tank is 20 inches long by 10 inches front to back. Multiplying the two numbers gives 200, then chopping off the last zero leaves 20 pounds of gravel, which does indeed cover about 2" on the bottom. A 55 gallon would be 48 x 13 = 624; chopping off the four leaves 62 pounds. If three inches of gravel is preferred (and that would probably look better in a large tank like the 55), add half again the amount (62 x 1.5 = 93 pounds for average three inches in the 55).

The crushed coral commonly used in saltwater setups is considerably less dense, so multiplying the aquarium length and height would yield almost three inches of gravel, rather than the two inches of the quartz or granite used in freshwater. Conversely, fine silica sand, which we probably shouldn't use anyway, is denser, and our magic number would probably yield only a little over one inch.

As far as the depth of gravel required goes, anywhere from none to about 6 inches can work, and is advocated by somebody or other. In most tanks, gravel is primarily decoration, and helps support other decor items such as rocks or driftwood. For this, two to three inches is generally sufficient. Shallow gravel lacks character and supporting power, and deeper gravel is hard to keep clean. Two to three inches is often the recommended gravel depth for tanks with undergravel filters as well.


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