how many actual gallons

robert teseo · Dec 26, 2017

is there any formula for pounds of rock displaces how many gallons? I have a 75 with over 100 lbs of rock, so how many gallons of water do I have? I,m sizing a chiller. I know there's not close to 75 in there

hijinks7 · Dec 26, 2017

There is no formula since different types of rock is more porous then other types. Even figi rock some is more porous then others. The only thing to do is fill up a bucket and put the rock in and see how much water it displaces then add it all up

Daniel@R2R · Dec 27, 2017

Seems like I saw a formula somewhere based on the number of pounds of rock involved. I agree with @hijinks7 that any such formula is going to be a rough estimate at best due to different rock densities and such. If you're looking for precision, measuring the displacement is about all you can do. I've never sought to be that precise...

robert teseo · Dec 27, 2017

i don't want to get that crazy, and I,m not going to disturb the tank so. to cover my behind, I,m buying the next size up chiller. it will be overkill, but mean no worries next summer

hijinks7 · Dec 27, 2017

If you have a 75g and 20g sump buy a chiller rated to 100g. Bigger is always better if you can afford it to the point its not cycling on and off too often.