50 gallon drum, how many "aquarium gallons"

[mike31154]

Also a remote possibility the difference between Imperial & US gallons may be a factor, depending on where the hardware is made.

[mike31154]

Originally Posted by Dearth

Very good explanation rock can displace a large volume of water
Half my 95 gallon tank is taken up by rock so at best I might have 50 gallons in it

To accurately determine volume of water displaced by rock or any submerged item you would need to weigh it.