We have built a fountain in our front garden and as part of the structure, there is a fish tank or aquarium at the base. I needed to estimate the volume of water in the tank so that we can accurately estimate the amount of any ammonia and so on that we need to use to keep the tank clean and the fish alive.

Here is my drawing of the tank: not so square and not so rectangular is it?

I needed to use the

- area of a rectangle
- area of a circle
- volume of a cylinder

This involved using two calculations using Pi, the mathematical constant that approximates to 22/7

Here is my spreadsheet:

I found very easily using an internet search how to convert cubic metres to Imperial Gallons but I wanted to enhance my spreadsheet so that it could be used as a template for other constants. This also explains why you can see Cu M in columns B and D … useful for drawing the two graphs from which you can take the trend line function as I did to calculate the cubic metres of water I was trying to find:

I can use the second graph to find the cubic metres in a body of water if I know the Imperial Gallons!

The Pi based formulas are:

area of a circle (please note, each of the circular ends of the aquarium are semi circles!) = PiR^2

= PI()*0.35^2

Volume of a cylinder: there are two of these and the are the foundations of the two fountain units = PiR^2H

= PI()*(0.45/2)^2*0.2

There you are, we have a 215 gallon aquarium that needs careful management now!

Download the spreadsheet from here volume_water_aquarium

Duncan Williamson

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