Does 42lbs Arragonite in 55 Gallon Mean Not 55 Gallons of water?

[Lbrdsoxfan]

People who drink it like wine?
People who drink beer slowly?
It can't be the Irish?

Got no time for that nonsense. Brown liquor is where it's at

 

[Lbrdsoxfan]

....

(I need to try ice in my beer next time.... )

Blasphemy!

 

[ilikefish69]

Is a pint of beer still a pint if you have ice?

what crazy person be putting ice in their beer ??!

 

[KStatefan]

You will have less the 55 gallons with nothing in the tank. Most manufactures use outside dimensions to calculate the volume.

 

[TheBear78]

If you can take the rocks out (I'm assuming it's not an established tank if you're considering draining it) you can simply measure the change in water level and calculate their volume based on the tank footprint.
For sand that would also work but it may be a bit too inconvenient. As an estimate, I would just work out the average depth and half it to account for the fact that the sand is saturated with water.
I'm sure that this would be close enough for dosing ratios etc.