Live rock displacement need help...

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Delatedlotus

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I need some help on figuring out exact water volume vs live rock displacement. I want to start carbon dosing soon, like today. But I have lbs and lbs of live rock and I don't know there weights or how much. 24 year old tanks, 129 gallon, 73 gallon, and a 100 gallon horse trough with sump in it (only half full). A little more than 3 inch's live sand. And ALOT of live rock.. How do I figure out rock water volume...? I
20201226_145529.jpg
n
20201226_145427.jpg
eed to be real close on the actual water volume.
 
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Delatedlotus

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I need some help on figuring out exact water volume vs live rock displacement. I want to start carbon dosing soon, like today. My phosphates and nitrates are very high right now. But I have lbs and lbs of live rock and I don't know there weights or how much. 24 year old tanks, 129 gallon, 73 gallon, and a 100 gallon horse trough with sump in it (only half full). A little more than 3 inch's live sand. And ALOT of live rock.. How do I figure out rock water volume...? I
20201226_145529.jpg
n
20201226_145427.jpg
eed to be real close on the actual water volume. Please if anyone can help me, it is greatly appreciated. Thank you
Not very good pictures here.. I will take some more with in the hour.. Thanks' for any help..
 

Hind

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Considering the type of rock you are using, it's not as simple as a weight-to-volume displacement because different types of rocks are more porous and hold water volume themselves.

Here is a picture from a BRS investigates video where they weighed retained water within different rock types.
1633284319918.png


Seawater weighs approx 2.5-3.5% (https://en.wikipedia.org/wiki/Seawater) more than freshwater due to the NaCl, etc. Given this reference above, if 1kg of rock retains 210g of water, then 22kg (approx 50lb) of rock might contain 4.6kg of water.

For every 50lb of rock = 4.6kg water = ~1.2 gallons

This isn't exact math, nor a simulation of your system. But you can see how this gets messy.

If it were me, I would take the total water volume size of the system (either known or take dimensions and calculate cubic inch volume). Back it off some to compensate for displaced water volume to rock/sand/equipment/etc and calculate a dose. I would go easy on the Carbon dose - the instructions should call for conservative dosing at first anyway. I've typed too much now... let us know what you did! Go Slow
 
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