Tank Size?

Length * Width * Height = Volume/231 = Volume in Gallons.

For my 30 for instance 36*12*16.5 = 7128/231 = 30.85 g

Thats a useful tidbit, but Goldfries has built a handy calculator for those who just aren't going to do the math. Will also convert to litres, Imperial gallons, etc.
 
Yes, our typical arrogance as Americans comes through again. We apologize to those who use Imperial Gallons.
 
Of course it depends on the size of the tank, but I use a quick one if the dimensions are fairly standard. Length X Width X Height in feet x 7.5. It is easy to remember and pretty easy to do. Of course, it gets rougher if you have strange dimensions (in inches,smaller tanks). Of course this is for us gallons.
 
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