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# Re: [Gravel] Formula

```> From: Zon Hisham Bin Zainal Abidin <zon at mad_scientist.com>
> Date: Mon, 23 Dec 1996 17:12:18 +0800
>
> Tank size 5' x 2' x 2'
>
> How do I determine the amount of gravel needed (in kilograms) if:

It depends on the characteristics of the gravel you use. As an
example, the "TexBlast" quartz gravel I use (2-3 mm grain size)
has a volume of 19 cubic inches per pound.  Figure the volume of the
gravel in cubic inches and divide by 19 to get the amount you need in
pounds.  Convert to whatever units you desire.

> 1)I intend to have a gravel height of 3" throught

Area of substrate is 60" x 24" = 1440 in^2
3" depth -> 3 in x 1440 in^2 = 4320 in^3
4320 in^3 / 19 in^3/pound = 227 pounds
227 pounds x 2.2 kg/pound = 500 kg

Hmmm, exactly 500 kg?  (OK, 500.21).  Odd coincidence?

Other substrate types will have different weight per volume, so you
may want to buy a sample and determine its characteristics.

BTW, the TexBlast displaces 2.4 gallons of water per 50 pounds.
That's useful to know when you figure true water capacity of a planted
tank system for accurate dosing of fertilizers and other stuff.

> 2)I intend to have a gravel height of 2" at the front and slopes
> gradually to 4" at the back of the tank?

Slightly more complicated math; same answer.

George
```