# Other Aquarium Forums > Marine Tanks >  8mm thick enough

## tawauboy

is a 200l tank of 18" height with glass thickness of 8mm sufficient to withstand salt water pressure?

thanks

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## kelstorm

one word.. NO!

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## tawauboy

kel,

thanks.
so what is the minimum recommended thickness?

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## VANAN

As far as i know, when a tank is taller then 14 inches it has be atleast half inch thick... I would say 12mm is a very safe range. 8mm is not strong enuff and your tank will bow and even tear apart.

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## nautilus

Hi,

I would presume you have a 3ft tank of dimensions 3x1.5.1.5 ft?
8mm is definitely enough for a saltwater aquarium. In fact, 6mm is already sufficient. Even taking into account the presence of saltwater, the pressure at the bottom will increase by only 10% at the most if we assume a specific gravity of 1.1 is used. The pressure at the bottom of the tank will be the highest at around 4900Pa.Take a look around at all the aquariums, most of them are using 6mm glass only. 8mm is good enough, 10mm will be better, 12mm is an overkill.

Naut

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## kelstorm

I would presume you have a 3ft tank of dimensions 3x1.5.1.5 ft?
8mm is definitely enough for a saltwater aquarium. In fact, 6mm is already sufficient. Even taking into account the presence of saltwater, the pressure at the bottom will increase by only 10% at the most if we assume a specific gravity of 1.1 is used. The pressure at the bottom of the tank will be the highest at around 4900Pa.Take a look around at all the aquariums, most of them are using 6mm glass only. 8mm is good enough, 10mm will be better, 12mm is an overkill.

Naut
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i beg to differ Nau.. IMO.... u need to consider the fact that some areas will not be the same pressure throughout.. for 6-8mm... i personally feel that it is too think... 10mm is what i would recommend coz i dun want to have the tank give way on me.. as such, my 4ft tank is using 12mm glass.. apart from safety margin, it looks nicer too... thinner glass seems to be very fragile to me...[: :Smile: ] and those aquarium that u seen outside is mostly catered to FW...
just my 2cents worth...

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## nautilus

> i beg to differ Nau.. IMO.... u need to consider the fact that some areas will not be the same pressure throughout.. for 6-8mm... i personally feel that it is too think... 10mm is what i would recommend coz i dun want to have the tank give way on me.. as such, my 4ft tank is using 12mm glass.. apart from safety margin, it looks nicer too... thinner glass seems to be very fragile to me...[:] and those aquarium that u seen outside is mostly catered to FW...
> just my 2cents worth... 
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Kel,

Glass is tougher than you think. I'll work out the details later. Even if some places have higher pressure than others, the shear modulus of glass (&amp;gt;30GPa) is more than enough to support the stresses encountered. Do you just "feel" that it's too thin due to your own judgement or just for aesthetics reasons? As mentioned earlier, it doesn't make much of a difference if it's fresh or saltwater. Many people out there THINK that having saltwater in the tank does make a tremendous amount of difference to the forces encountered in the tank, well the truth is no! I was overestimating when i stated a SG of 1.1 for saltwater, let's take the high side of the norm that is 1.026, that will only work out to be 2.6% heavier than freshwater. Is that a big deal of weight, no. 8mm is definitely more than enough for a marine tank. Those 6mm glass tanks that i saw are mostly in SW LFS, so no dispute about that. Most of the time, however, the silicon seals tend to give way before the glass which largely depends on workmanship rather than glass thickness. But making an arguement based on glass thickness alone is plainly unjustified. I do agree for a 4 feet tank, 10mm or even 12 mm glass should be used. The reason being mainly because of the lateral forces at the sides associated with the length of glass, this is assuming the bottom is well supported. However, for a 3ft, 12mm is an overkill. 10mm would be good to prevent condensation and 8 mm would be the most cost effective.

Naut

Naut

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## tawauboy

my tank is eheim, think is the mp series.
dimension, 3.5'x15"x18".
no centre brace but there is 2 strips of glass runnig across the front and back panel.
bottom of tank is supported at the rim only, centre of tank is off bottom.

i plan to have some rocks and fishes.
advice pls.

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## DragonGoby

Hey, get as thick a tank as you can!! See my previous post on my tank going berserk... Thanks guys, for replying to my calls for help.  :Smile:  I've re-glued the tank, so now it's like chiam si tong. I'm now eyeing this 4-foot acrylic bow front tank with rather ok-thickness planes. Anyone's bought this before? Clementi block 328 is selling this with it's cabinet at about $600 - sounds rather a good deal. Birthday's coming, but I doubt my parents are going to get me a fish tank for a birthday present though (hint hint... I'll be damn good friends with ya if you're gonna get me that!  :Wink:  ). With 5 large tanks and numerous smaller ones at home mommy and daddy aren't too eager to get me any more, hahaha!! 

Just get about 10mm, think you'll be quite safe with that, although more isn't bad either. Weigh out the costs vs benefits and see if the opportunity cost is paid off by thinner glass. 

Regards,
Hong Yee

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## nautilus

tawauboy,

I think eheim is using tempered glass for their tanks if i'm not wrong. If it's the case, then the effective yield strength of tempered glass is even higher. Therefore, 8mm would more or less be the equivalence of 10mm of normal glass

Dragongoby,

I read your post regarding the bowing of your tank. 6mm for a 4ft is definitely to thin. I'm sure the bowing wouldn't have happened even with 8mm glass, although the recommended thickness for a 4 ft is 10mm. For a 3ft, 8mm will do fine. 10mm 3 footers are better, but they are also much more expensive as compared to a 8mm 3ft. Based on the quotations given by various dealers, a 10mm 3ft isn't very much cheaper than a 10mm 4 ft. So if you've the money to spend, why not go straight to a 4 ft. I do agree that thicker is better, that's common sense, but one should not go OTT in their choices right. If not isn't 15 mm glass even better? What about 30mm glass? Or just make it 45cm glass....the equivalence to the width of your tank. The bow tank that you're looking at would probably come with 10mm glass, which is the norm for a 4 footer.

Naut

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## tawauboy

my tank bottom does not lie on surface top.
basically, the tank is supported by the rim.
can it take the weight of rocks?

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## nautilus

taqauboy,

In that case, see if you can get a piece of 10mm glass the size of the base. Put it under the base of the tank, followed by a piece of styrofoam to even out the pressure, and the tank. That's the most cost effective method i can think of at the moment. Also, do check that the edge of the cabinet protrude far enough to support the tank. Do take into account the accidental spillage that you may have occasionally on the edge of the tank which may result in the weakening of the support ledge. 

Naut

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## tawauboy

thanks

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## Natquarium

Hi guys,

Any recomenation on the thickness of glass for each tank of 1)3x1.5x2ft tank, 2)3x1.5x2.5ft tank and 3)5x2x2.5ft tank? I am talking about with all 3 tanks without bracing.

Thanks

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## kelstorm

Any recomenation on the thickness of glass for each tank of 1)3x1.5x2ft tank, 2)3x1.5x2.5ft tank and 3)5x2x2.5ft tank? I am talking about with all 3 tanks without bracing.
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1)3x1.5x2ft tank = 10mm
2)3x1.5x2.5ft tank = 10mm
3)5x2x2.5ft tank = 12-15mm

This thickness, IMO, is safe and look nice too... but due to the thickness, it is quite ex...[ :Grin: ]

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