# Re: NFC: Re: Filterless Aquariums.

```Sajjad, the correct number is 231. :)  Inches/231 = Gallons.

Second, gravel/sand does NOT displace the volume of it.  There's space
between teh grains, which is filled with water.  Figuring out the volume
isn't easy, and differs on the type -- bigger grains, less volume per
lb. An easy way to figure it out:  Fill a five gallon bucket with the
desired media (smaller is okay, too) and fill it to the brim with
water.  Pour the water carefully out into a container, and you'll get
the ammount of the volume that is NOT gravel.  So, if you get one
gallon, five gallons of media actually is four gallons of media.

Josh.

>
> On Fri, 9 Feb 2001, Gary Rollwage wrote:
> > How much  (on the average) does gravel, plants, etc etc. displace
> > the amount of water in a tank?
>
> Hi folks,
> Haven't read all NFC mail in a week, so, apologies if this has been
>
> I presume that plants would displace only a small amount of water. Even if
> you have a lot of plants, you aren't loosing too much of water volume.
>
> I also presume that stones, sand and gravel would displace the about same
> amount of water as their volume. Multiply the length and depth of the tank
> with the height of the gravel to get the volume displaced (in cubic inches
> of you are using inches as the measure).
>
> There should be a standard conversion from cubic inches to gallons which I
> don't know. Here is an approximate attempt: A cubic inch is equivalent to
> 16.4 cubic centimeters (cc) and there are 1000 cc in a liter. Assuming
> 3.75 liters per US Gallon, we have about 3750 cc to a US Gallon or about
> 229 cubic inches to a US Gallon.
>
> Assuming that you have 3" of substrate in a 55 Gallon (3x1 ft base), you
> would then have 3 x 36 x 12 or 1296 cubic inches or about 5.6 Gallons of
> substrate. Approximating further, each inch of substrate in a 55 Gallon
> tank would displace about 1.5 to 2 gallons of water.
>
> Again, these numbers are all approximations. If anyone has better numbers,