I have done alot of research on building large aquariums, mostly because i plan on building one. This is some information that i have gathered that i think would be useful to some poeple designing thier tank that they might not know or think about.

7.48 Gallons will fill 1 cubic foot of space(1,728 cubic inches)

1 gallon of water weighs approximately 8.35lbs

the taller the tank the more water pressure that will be on the sides and bottom.
to find pressure on bottom
water weight divided by surface area in inches equals psi on bottom
to find side pressure
water weight divided by surface area of the side in inches, then divide that by 2 and it is your average pressure.

that should give you enough information to decide what materials you would want to use.

i could be wrong, but this is the information that i was able to gather with online resources and civil engineers that i have worked with through my construction company.

this helped a bit, as i too want to build my own tank.

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30 gallon tank = about 300lbs thats alot! sorry kind of random

It might be easier to calculate at 231cu inches to the gallon. Most of us measure our tanks in inches (In the US anyway.)

HxDxW=cu inches of tank

cu inches of tank/ 231=g capacity

g x 8.337=water weight

Now you need to add the weight of the tank, stand, and equipment to get an idea of just how much weight is on one small area of your floor.

I mention this just so people are thinking about the amount of weight on a wood framed floor.

Some people should probably reinforce the floor under their tanks.

I just made an excel sheet to do the calculations of weight, pressure, and forces on each side of the tank if anyone wants it.
This is a copy and paste from the sheet, you enter the dimensions in inches and it gives the results.

Aquarium Forces and Weights

Depth (front to back) 18.5
Height (tall) 20
Long (width) 36

Water Capacity 57.66233766 gallon
Water Weight 480.7309091 lbs.
Bottom Pressure 0.721818182 PSI
Force on front or back 259.2 lbs.
Force on end panel 133.2 lbs.

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"Republicans believe every day is the Fourth of July, but the democrats believe every day is April 15. "-Ronald Reagan

DavidC,
I am new to the forum but I believe your excel sheet would help me a lot. Trying to build my own tank and the plug and play would save me a lot of time.