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Discussion Starter · #1 ·
hi new to saltwater/reef tank. began my set up after preliminary research. Went to local store and purchased six 4.4 gallon (= 26.4 gallons) RO DI water jugs bc i read biocube tend to take less than stated amount plus water displacement. filled it with four jugs added 30 pounds sand and about 25 pounds live rock and it's totally full. how can that be? I've read on forums 26 gallons 25 gallons even 22 gallons but 17 gallons? any thoughts? any help would be greatly appreciated.
 

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Salt Viking
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The displacement of Aragonite is 24.6lbs per 1 displaced gallon of seawater.

And Silica Sand is about 22.2lbs per 1 displaced gallon.

So some quick calculations will give you your total volume available.

25lbs rock = 1 Gallon of saltwater

30lbs (Assuming arragonite) sand = 1.22 Gallons of saltwater

So your rock and sand displace 2.22 gallons of water.

And if you filed it with four 4.4 gallon jugs equaling 17.6 gallons. Then your total in tank volume should be 19.82 gallons..

Hmmmmmmm..... Don't know what to tell you there..
 

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Aquatic Philosopher
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sounds plausible.

This is one reason why I advocate for minimalist rock/sand. In small nano tanks, you should use as little rock (and sand) as possible as every gallon counts.
 

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Aquatic Philosopher
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The displacement of Aragonite is 24.6lbs per 1 displaced gallon of seawater.

And Silica Sand is about 22.2lbs per 1 displaced gallon.

So some quick calculations will give you your total volume available.

25lbs rock = 1 Gallon of saltwater

30lbs (Assuming arragonite) sand = 1.22 Gallons of saltwater

So your rock and sand displace 2.22 gallons of water.

And if you filed it with four 4.4 gallon jugs equaling 17.6 gallons. Then your total in tank volume should be 19.82 gallons..

Hmmmmmmm..... Don't know what to tell you there..
Not bad for ball-parking...

but be careful with mass and volume equations... it really is apples to oranges as different density rock can displace different volume despite the same weight.
 

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Salt Viking
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Not bad for ball-parking...

but be careful with mass and volume equations... it really is apples to oranges as different density rock can displace different volume despite the same weight.
I ran the calculations against the estimated specific gravity of aragonite and silica. I would give it a loose margin of error in terms of reality. That rock and sand could easily displace between 2 and 4 gallons of saltwater. I mean you never know the internal structure of the rock. You would really need to do a displacement test on every piece of rock to find out for sure.

I just don't know why the numbers for the tank are so far off.. I can't see that rock and sand displacing 13 gallons. I have almost twice that and I could definitely fit it all in two 5 gallon buckets then pour water in..
 

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Aquatic Philosopher
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Yes, it was a good ballpark calc. Factor in any air that might be trapped in the rock lattice structure or less dense rock and potential differences in aragonite sand. I have seen differences between crushed coral sized substrate and oolite, especially in new tanks. Depending on what he has, any additional air displacement, I have seen surprising little water in some heavily rock/sand-ed tank.
 

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Aquatic Philosopher
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no replacement for displacement... :lol:
 

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hi new to saltwater/reef tank. began my set up after preliminary research. Went to local store and purchased six 4.4 gallon (= 26.4 gallons) RO DI water jugs bc i read biocube tend to take less than stated amount plus water displacement. filled it with four jugs added 30 pounds sand and about 25 pounds live rock and it's totally full. how can that be? I've read on forums 26 gallons 25 gallons even 22 gallons but 17 gallons? any thoughts? any help would be greatly appreciated.
I had approx. 18-19 gallons of water in my 29 biocube when I had a full sand bed, and 21lbs of live rock. Now I have about 30lbs of live rock, and am just about bare bottom (2 more water changes), and I think I've only gained approx a gallon or two...
 

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Discussion Starter · #12 ·
thanks for the answers

i was instructed to fill the tank 5/8 full while totally empty and mix in the salt using the Koralia to help with dilution. i put in three 4.4 gallons into empty tank and was already about 5/8. so yes 17 gallon included rear chamber. I'm not upset just confused. the jugs are definitely 4.4 the tank is supposed to be 29. there is a huge discrepancy. Even at the higher estimations of water displacement I'm still missing water and my floor is dry so its not leaking out.
 

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Aquatic Philosopher
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The tank might be about 29g if it was completely empty (even the false wall removed) and brimmed to the very top. Surprisingly, most tanks of often not quite what they claim to be.
 

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Discussion Starter · #14 ·
i called oceanic

the technical rep there told me oceanic biocube 29 is not 29 gallon its size 29 which means of you would build a glass box around the entire tank i.e lid, bottom and all four sides that box would hold 29 gallons. honestly i dont even think thats the case but he gave me an honest direct answer. thanks all of you for the help.
 

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Aquatic Philosopher
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Ahhh, so if you seal the tank, it would displace 29g worth of volume... someone should sue.
 

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no replacement for displacement... :lol:
As an owner of a fire breathing 6.2L V8, I can surely attest to this adage :thumbup:

Also, i've found that your standard rectangle aquariums can be under rated. For example, a 10G is 2400 cubic inches (20x12x10), which equates to roughly 10.4 gallons. that is if you filled it to the brim. A 40 Breeder at 36 x 18 x 16 technically is 44 gallons.
 
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