FYI: water displaced by dry rock

Victor_C3 · Feb 7, 2020

I don’t know if this will be if any help to anyone planning a system.

I just added 140 pounds of dry rock to my aquarium. It displaced 9.5314 gallons of water. Do the math and roughly 1 pound of dry rock will displace .068 gallons of water or it takes approximately 14.69 pounds of dry rock to displace 1 gallon of water.

The rock added came from here:

https://www.marinedepot.com/aquamaxx-dry-live-rock-by-marco-rocks

Ron Reefman · Feb 7, 2020

Interesting info! I'll round it off and say 150 lbs of rock displaces 10 gallons of water.

Cell · Feb 7, 2020

It seems to me this is going to completely depend on how porous or dense the rock is. Pukani vs Fiji or Marco rock for instance would be significantly different, I think.

xxkenny90xx · Feb 7, 2020

Very interesting, thanks!

MarineMalecki · Feb 7, 2020

sounds like a good topic for a @BRS video

iron_mike_gt · Feb 7, 2020

Cell said:
It seems to me this is going to completely depend on how porous or dense the rock is. Pukani vs Fiji or Marco rock for instance would be significantly different, I think.

Correct. You would need to know the density of the rock in order to calculate displacement in this manner. Mass is the weight of the object; volume is the amount of space the object takes up. Density = Mass / Volume

This is the same as with people - two people can weight the same, but the one with more muscle (denser than fat) will take up less space, and thus displace less water in, say, a bath tub.