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The camaro loving reefer
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Discussion Starter #1
how much rock will my 55 gallon hold.Or how much would the weight will the bottom pane of glass hold?
 

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Reefer and proud of it!!!
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Ok I have a question about this thread. Knowing that glass tanks have the bottom pane about a half inch from the bottom and acrylic tanks have the bottom pane flat on the bottom completely supported where as the glass tanks are almost completely supported on the edge if not some times in the center cross bar.
 

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Aquatic Philosopher
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They will hold a lot but they don't like to absorb a shift in weight... so avoid any sharp pressure points and any shock. ;) :doh:
 

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Reefer and proud of it!!!
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well i meant that doesn't the glass have a limit of some sort, being that the bottom pane is mostly being held in place with the silicone. yes the plastic frame does add a little support.

I know my old 120 gallon i had was yes a used tank. and old because the plastic was completely decorative and that the tank it self had no center brace on the top. so old that the plastic just came off when i was moving it around. when i finally setup the tank there was no plastic on top or bottom because like i said no support just decoration. the bottom pane of glass was just supported by just the silicone. i have heard of people putting styrofoam in the empty space. helping support the bottom pane. course i didn't know that until after the tank was setup. I had the tank up and running with no problems until i had added about 50 extra pounds of rock on top of the the 60 or 70 already in there and then the next morning i had a leak in the bottom back seal. i think it was mostly when i was moving the rocks the rocks banged the bottom pane a little to hard not so much the extra pounds.
 

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Aquatic Philosopher
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it is better for the bottom pane to be "floating" of you will because glass done not like that point pressure source. The frame can actually help keep the seam integrity and combined with age, I am guessing that is what happened. But yes, it does have a limit but it is very unlikely to reach it if it is evenly distributed to the edge and down.
 

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Water=997kg/m^3 @ 25C. Salt Water=(1.025)(997)= 1022kg/m^3 (density of reef water @ 25C).

55gal X (231in^3/gal) = 12705in^3. 12705in^3 X (m^3/61024in^3) = 0.208m^3 (volume of your tank).

0.208m^3 X (1022kg/m^3) = 212.777kg of water in your tank.

Force=(mas)(acceleration).
F=(212.777kg)(9.807m/s^2) = 2086.705 Newtons. 2086.705N X (lbf/4.448N) = 469.555 lbf (weight of your tank full of water.)

If the bottom plate is approx 48" X 13" there is a pressure exerted of (469.555 lbf) / (624 in^2) = 0.752 lbf/in^2...pretty light.

Of course you could have just said: water = (8.345 lbs/gal) X (55 gal) X (1.025 SG) = 470.449 lbf. But I thought you might want to know about the 1 lb difference. Plus I'm warming up for homework.

Engineers use what is called a factor of safety in all design work. It is defined as (critical load)/(applied load). If FOS=1, you will experience failure. In many cases, designs will have a FOS=2 which in this case means that the critical (failure) load = 2 X 469.555 = 939.111 lbf!

The point is, I think at most you're gonna add 100 lbs of LR which is only ~ 20% of what you could do with a FOS of 2. I would really need to analyze the support system and know the holding stength of silicon and the critical stress of your glass to give an exact FOS, but as others have said, stay away from shock and applying all weight in one or two areas, and you should be fine.
 

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There was a you tube video showing a guy stacking bricks in a 20g tank. I believe he had it up to 250lbs and then he stood on the bricks. It didn't break. I believe he then laid a sharp piece of brick and stood on it. It broke. The point - futureDoc is right. It's about pressure points.

I locked my keys in the car one time, and tried to break a side window with a rock. It didn't budge. I took a screw driver and hit it with a rock against the glass and it shattered.
 

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The camaro loving reefer
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Discussion Starter #13
my dad just built his first skyscraper. i was there one day, and he took a 3lb hammer and threw it as hard as possible at a pane of glass. it did not even leave a mark. however he just taped it on edge and the hole thing shattered. so i guess it just how glass is.
 

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my dad just built his first skyscraper. i was there one day, and he took a 3lb hammer and threw it as hard as possible at a pane of glass. it did not even leave a mark. however he just taped it on edge and the hole thing shattered. so i guess it just how glass is.
A hallmark of tempered glass.
 

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Aquatic Philosopher
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About 8 years ago, my brother attempted to catch a closing door on my old '79 280ZX by the glass window and it shattered in his hand (the Z did not have the metal rim around the window, a nice feature up til that point). Still glass is dependent on a lot a factors before the fail point is reach.... mostly it is not shock resistant but can hold a lot of weight for as long as it does not shift quickly into it.
 

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The camaro loving reefer
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Discussion Starter #16
i had the same thing happen to my 91 camaro. you notice how it could never happen to us. bad things only happen from the passengers.
 

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About 8 years ago, my brother attempted to catch a closing door on my old '79 280ZX by the glass window and it shattered in his hand (the Z did not have the metal rim around the window, a nice feature up til that point). Still glass is dependent on a lot a factors before the fail point is reach.... mostly it is not shock resistant but can hold a lot of weight for as long as it does not shift quickly into it.
This is very true. When I did all those calcs before, it was just to show overall strength. It was for a static system. It all basically comes down to force-time (shock), and force-area relations (pressure).
 
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