Calculations for the Aquarium Weights

Weight of water is 8.34 pounds per gallon.  (Assuming pure H₂O at sea level)

Density of any material is defined as the weight per unit volume.

Density of water is 62.4 pounds per cubic foot (pcf)

Density of rock varies approximately as follows: Granite = 175 pcf, Limestone = 165 pcf, Sandstone = 147 pcf, Shale = 170 pcf

There is the weight of the water, the aquarium itself and the weight of the rocks and substrate and stand.  You know that the density (weight per unit volume) of rock is greater than the density of water.  That's why the rock doesn't float.  Depending upon the rock that you use, the density might vary from 120 pounds per cubic ft (pcf) to 180 pcf.  The all-glass web site says that a 125 gallon tank weighs 206 lbs (empty) and the total estimated weight of a full aquarium is around 1400 lbs.  Let's say that you are adding 210 lbs of limestone rock and gravel to a tank.  The density of limestone is around 140 pcf.  If this was a solid rock it should be around (210 lb/140 pcf = )1 1/2 cubic ft in size.  If it were all gravel it would not all fit into a 1 1/2 cubic ft box but that is because there are lots of pockets of air in that cube of gravel.  So 210 pounds of limestone whether solid or gravel should displace about 1 1/2 cubic ft of water.  The "bouyant weight" of rock is the weight of the rock minus the weight of the water that it displaces.  So this rock has added about (1.5)(140-62.4) = 116 pounds to the aquarium weight.  The water in the aquarium weighs (125)(8.34) - (1.5)(62.4) = 950 pounds.  So if that aquarium stand weighs 44 pounds, then this is how this works out.  Total weight = 206 lb (tank) + 950 lb (water) + 210 lb (rocks) + 44 lb (stand) = 1400 lbs.  (Note that since I subtracted out the volume of water that is displaced by the rock, I

4 ft (123 cm) long aquariums
(This is a conversion from standard US aquarium sizes and may not represent standard European aquarium sizes)
English units				metric units
US gallons	UK gallons	dimensions	weight	liters	dimensions	weight
33 long	27.5	48 1/4" x 12 3/4" x 13 3/8"	382 lb	125 liter	123 cm x 32 cm x 34 cm	173 kg
40 long	33	48 1/4" x 12 3/4" x 16 7/8"	455 lb	151 liter	123 cm x 32 cm x 43 cm	206 kg
45 long	37.5	48 1/4" x 12 3/4" x 19"	510 lb	170 liter	123 cm x 32 cm x 48 cm	231 kg
55 gallon	46	48 1/4" x 12 3/4" x 21"	625 lb	208 liter	123 cm x 32 cm x 53 cm	284 kg
60 gallon	50	48 3/8" x 12 7/8" x 23 7/8"	710 lb	227 liter	123 cm x 33 cm x 59 cm	322 kg
75 gallon	62.5	48 1/2" x 18 1/2" x 21 1/8"	785 lb	284 liter	123 cm x 47 cm x 54 cm	356 kg
80 X-high	66.5	48 7/8" x 14" x 30 3/4"	990 lb	303 liter	124 cm x 36 cm x 78 cm	449 kg
90 gallon	75	48 1/2" x 18 1/2" x 25 5/8"	1050 lb	341 liter	123 cm x 47 cm x 65 cm	476 kg
110 X-high	91.5	48 1/2" x 18 1/2" x 30 1/2"	1320 lb	416 liter	123 cm x 47 cm x 78 cm	599 kg
120 gallon	100	48 1/2" x 24 1/2" x 25 1/2"	1400 lb	454 liter	123 cm x 62 cm x 65 cm	635 kg
150 X-high	125	48 1/2" x 24 1/2" x 30 1/2"	1800 lb	568 liter	123 cm x 62 cm x 78 cm	817 kg

This site give you a list of common tank sizes and approx total weights=>

http://www.alysta.com/books/fishtank.htm    or   http://www.all-glass.com/services/techinfo.shtml

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