water displacement?

['Sapphire']

Is there any way of telling how much water is displaced in a tank by live rock?
Like a formula between pounds and gallons

[Nullig]

It's going to vary by the type of rock, i.e. how porous it is.

[bubbletip]

You need to know what type of rock you have and post that then someone could give you a ballpark idea.

['Sapphire']

75 lbs of fiji in 80 gals thankyou

[Wolverine]

You could remove all of the rocks from the tank, and then see how much water it takes to fill it back up. IMO, it wouldn't really be worth the effort, but you could do it that way.

Dave